Posted – July 1st, 2010
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Nutrients

There are about 15 elements known to be essential to plant life. Carbon, hydrogen, and oxygen are absorbed from air and water. The remaining 12 elements are absorbed primarily from the soil, in mineral (inorganic) forms such as NO3- and K+. They constitute a natural part of soil that becomes available to the plant os organic matter decays and soil particles such as sand and clay dissolve.

Soil elements that are necessary for normal growth are called nutrients. The elements nitrogen (N), phosphorous (P), and potassium (K) are considered major nutrients. The three numbers that appear on all fertiliser packages give the available percentage of these three nutrients that the fertiliser contains; and always in the order N-P-K. For example, 10-2-0 means 10 percent N, 2 percent P (actually, 2 percent P2O5), and no K (actually, no K2O). Fertility is often measured by the amounts of major nutrients a soil contains. Relatively large amount of N-P=K are needed for lush growth.

Three other elements – calcium (Ca), sulphur (S), and magnesium (Mg) – are called secondary nutrients. Plants require less of these nutrients, and most cultivable soils contain adequate amounts for good growth.

Six remaining elements are called trace elements or micronutrients. As their name implies, they are needed in very small amounts. Commercial soils contain enough trace elements to sustain normal growth. The trace elements are also present in manures, humus, ash, and limestone.

Nitrogen

The amount of nitrogen a soil can supply is the best indication of its fertility. Nitrogen, more than any other soil nutrient, is inextricably linked with the living ecosystem. Nitrogen is continually cycled through living systems: from soil to plants and back to the soil, primarily by the activity of soil microorganisms. Nitrogen is essential to all life. Nitrogen is a key element in the structure of amino acids, the molecules which make up proteins. These, and all other biomolecules, are synthesised by the plant. Chlorophyll, genetic material (for example, DNA), and numerous enzymes and plant hormones contain nitrogen. Hence, N is necessary for many of the plant's life processes.

Cannabis is a nitrophile, a lover of nitrogen. Given ample N, Cannabis will outgrow practically and plant. Ample nitrogen is associated with fast, lush growth, and the plant requires a steady supply of nitrogen throughout its life. Marijuana's requirements for N are highest during the vegetative growth stages.

Phosphorous

P is a constituent of energy-transfer compounds such as NADP and ATP, and molecular complexes such as the genes. The energy compounds are necessary for photosynthesis, respiration, and synthesis of biomolecules. Cannabis takes up large amounts of P during germination and seedling stages. During flowering and seed set, Cannabis' need for phosphorous is also high.

Potassium

K influences many plant processes, including photosynthesis and respiration, protein synthesis, and the uptake of nutrients. Just as with P, K uptake is highest during the earliest growth stages. K is associated with sturdy stems and resistance to disease in plants.

Calcium

Ca functions as a coenzyme in the synthesis of fatty compounds and cell membranes, and is necessary for normal mitosis (replication of cells). Plants take up much more Ca than the small amount necessary for normal growth. Ca is not added to soil as a nutrient; is added to adjust the soil's chemistry or pH.

Sulfur

S is a constituent of certain amino acids and proteins. It is an important part of plant vitamins, such as biotin and thiamine, which are necessary for normal respiration and metabolism. (Plants synthesise all vitamins they need.) Most soils suitable for growing marijuana contain plenty of S.

Magnesium

Mg is involved in protein synthesis and metabolism of carbohydrates. Mg is the central element in the structure of chlorophyll molecules and hence has an important role in photosynthesis. Most mineral soils and commercial soils have a good supply of Mg.

Trace Elements

The trace elements (Fe, Mn, Mb, B, Cu, Zn) are particularly important in the coenzymes and catalysts of the plant's biochemistry. Many life processes, particularly the synthesis and degradation of molecules, energy transfer, and transport of compounds within the plant, depend on trace elements. Trace elements are not used in large quantities to spur growth, but are necessary in minute amounts for normal growth. Indoor soils rarely require an addition of trace elements.

All the nutrients are needed for normal growth. However, most of them are supplied by the potting soil. Ca, S, and the trace elements rarely present any problems. For most growers, fertilising will simply require periodic watering with a complete fertiliser, one that contains N, P, and K.

Application: Fertilising

To grow to a large size, marijuana requires a steady supply of nutrients. These can be added to the soil before planting or anytime during growth. Bulk fertilisers are added while the soil is mixed, as described in section 6. These include manures, composts, humus, and concentrated fertilisers, such as rose food. Once the plants are growing, never condition or mulch indoor soils with bulk fertilisers. they promote moulds and fungi and attract other pests to the garden. Concentrated fertilisers can damage the plants if they come in direct contact with the stem or roots.

While the plants are growing, nutrients are given in solution; they are dissolved in water, and the plants are watered as usual. Soluble fertilisers can be either organic or inorganic (chemical), and come in a wide range of concentrations and proportions of nutrients. Two organic fertilisers are liquid manure (about 1.5-1.0-1.5) and fish emulsion ((Some fish emulsion may contain whale by-products.)) (about 5-1-1). Chemical fertilisers commonly may have 20-20-20 or 5-10-5, or may contain only one nutrient, such as 16-0-0.

A 10-5-5 fertiliser is 20 percent soluble nutrients and 80 percent inert ingredients. a 30-10-10 has 50 percent available nutrients and 50 percent inert ingredients. There is approximately the same amount of N in one tsp. of 30-10-10 as in three tsps. of 10-5-5.

Actually, you can almost use any fertiliser, but the nitrogen content should be proportionately high, and there should be some P and L also present. For example, a 20-20-20 would work fine, as would a 12-6-6 or a 3-4-3, but not a 2-10-10 or a 5-10-0.

How much fertiliser to use and how often to fertilise depend primarily on the fertility of the soil and the size of the container relative to the size of the plant. Small plants in large pots usually do not need to be fertilised. Even in small pots, most plants do not need to be fertilised for at least the first month.

As the plants grow, they take nutrients from the soil, and these must be replaced to maintain vigorous growth. During the vegetative stage, even plants in large pots generally require some fertilising, particularly with N.

The rate of growth of indoor plants is usually limited by the amount of light and space, once adequate nutrients are supplied. At this point, an increase in nutrients will not increase growth. Your goal is to supply the plants with their nutritional needs without overfertilising and thus toxifying the soil.

Most fertilisers are designed for home use and have instructions for fertilising houseplants. Marijuana is not a houseplant, and it requires more nutrients than houseplants. The extra nutrients that it needs may be supplied by the use of large pots and a fertile soil mixture. In many cases, you will need to fertilise only in the dosages recommended on fertiliser packages for houseplants. For instance, Rapid-Gro (23-19-17) is popular among marijuana growers; use one tablespoon per gallon of water every two weeks.

A typical program for fertilising might be to fertilise during the fifth week of growth and every two weeks thereafter until flowering. Then discontinue fertilising (or give at one-half concentration) unless the plants show a definite need for nutrients. It is better to fertilise with a more diluted solution more often than to give concentrated doses at longer intervals. (For instance, if instructions call for one tablespoon of fertiliser per gallon once a month, use one-quarter tablespoon per gallon once a week.)

Make sure that a fertiliser is completely dissolved in the water before you apply it. Put the recommended amount of fertiliser in a clear glass bottle and mix with about one cup of water. Shake vigorously and then allow it to settle. If any particles of fertiliser are not dissolved, shake again before adding the rest of the water. If you have difficulty getting all the fertiliser to dissolve, first add hot top water. If the fertiliser still does not completely dissolve, you should use another fertiliser.

Never fertilise a dry soil or dry Soilless medium. If the medium is dry, first water with about one-half quart of plain water per pot. Let the pots sit for about 15 minutes so that the water is evenly dispersed in the pot. Then fertilise as usual.

It is difficult to give instruction for fertilising that will cover all garden situations. You want to supply the plant with its nutritive needs, but overfertilising con toxify the soil. Fertilising according to instructions for houseplants (both in frequency and concentration) should not toxify the soil. However, the plants may sometimes require more frequent or more concentrated fertilising. A good way to judge the plant's needs is not to fertilise one plant, double the fertiliser of another plant, and give the rest of the plants their normal dose. If the unfertilised plant grows more slowly, or shows symptoms of deficiencies, then probably all the plant are depending on soluble fertilisers and must be fertilised regularly. If the plants receiving the double dose grows faster than the other plants, increase the other plants' supply also. On the other hand, if there is little difference among the plants, then the soil is providing the plants with enough nutrients, and they either should not be fertilised or should be fertilised with a less-concentrated solution.

Because they are grown in a relatively small area, it is easy to overfertilise indoor plants. When plants are vigorous, look healthy, and are growing steadily, don't be anxious to fertilise, particularly if you have already fertilised several times with soluble fertilisers. Slow growth or symptoms of deficiencies clearly indicate the need for fertilising.

Overfertilising

In an effort to do the best for their plants, some people actually do the worst. Overfertilising puts excessive amounts of nutrients in the soil, causing toxic soil conditions. Excessive amounts of one nutrient can interfere with the uptake of another nutrient, or change normal plant-soil relations. Since it takes time for a build-up to occur high concentrations of nutrients generally encourage excellent growth until the toxic level is reached.

It takes less N than other nutrients to toxify the soil; hence there is less margin for error when using N. Too much N changes the osmotic balance between plant and soil. Instead of water being drawn into the plant, water is drawn away and the plant dehydrates. The leaves feel limp even though the plant is well watered. The plant will soon die. This tips of the leaves die first and very rapidly the leaves change colour, usually to gold, but sometimes to a brown or green-grey. This change in the plants is faster, more dramatic, and more serious than for any kind of nutrient deficiency.

You can save the plants by immediately leaching the pots as soon as the condition is recognised. Place the pots outdoors or in a sink or bathtub. Discard the top inch or two of loose dirt. Run lukewarm water through the soil until a gallon of water for each two gallons of soil has passed through each pot. The leaves recover turgor in one or two days if the treatment works.

Foliar Feeding

Foliar feeding ((Nitrogen fertilisers are usually NO3 (nitrate) or NO2 (nitrite), substances which are also used to preserve food. They have been shown to undergo reactions to form carcinogenic substances (nitrosamines). As with eating food treated with nitrates and nitrites (hot dogs, sandwich meats, etc.), there is a possibility that such substances might be ingested by eating or smoking foliar-fed plants.)) (spraying the leaves with fertiliser) is a good way to give the plants nutrients without building up the amount of soluble substances in the soil. After the first month, foliar feed the plants with, for example, fish emulsion or a chemical fertiliser. Use any fertiliser that states it can be used for foliar feeding even if it says "not recommended for foliar feeding houseplants." Use a fine-mist sprayer, such as a clean Windex or Fantastik bottle. Dilute the fertiliser according to directions (fish emulsion at one tablespoon per gallon) and spray both sides of the leaves. When foliar feeding, you should spray the plants with plain water the next day, to dissolve unabsorbed nutrients and clean the plants.

Foliar spraying is also a good way to treat plants suffering from nutrient deficiencies. Some nutrient deficiencies actually are caused by the soil's chemistry, rather than by the absence of the nutrient in the soil. Addition of the necessary nutrient to the soil may not cure the plants' problem, because the nutrient becomes locked in the soil, or its uptake may be limited by high concentrations of other elements present in the soil. Foliar feeding is direct, and if the plant's deficiency symptoms do not begin to clear up, then the diagnosis is probably incorrect.

Nutrient Deficiencies

Before Diagnosing

Before you assume the marijuana plant has a nutrient deficiency, make sure the problem is not due to other causes. Examine the marijuana plant leaves, and along the stem and in the soil.

Even under the best conditions, not all leaves form perfectly or remain perfectly green. Small leaves that grew on the young seedling normally die within a month or two. Under artificial lights, bottom marijuana leaves may be shielded from the light, or be too far away from the light to carry on chlorosynthesis. These leaves will gradually turn pale or yellow, and may form brown areas as they die. However, healthy large leaves should remain green at least three to four feet below the plant tops, even on those plants under small light systems. Under low light, the lower-growing shoots as well as the large leaves on the main stem are affected. Some symptoms of nutrient deficiencies begin first at the bottom of the plant, but these symptoms generally affect the lower leaves on the main stem first, and the progress to the leaves on the branches.

Although some deficiency symptoms start on the lower, older leaves, others start at the growing shoots or at the top of the marijuana plants. This difference depends on whether or not the nutrient is mobile and can move from the older leaves to the active growing shoot. Deficiency symptoms of mobile nutrients start at the bottom of the plant. Conversely, deficiency symptoms of immobile nutrients first appear on the younger leaves or growing shoots at the top of the plant. N, P, K, Mg, B, and Mb are mobile in the plant. Mn and Zn are less mobile, and Ca, S, Fe, and Cu are generally immobile.

A dry atmosphere or wet soil may cause the blade tips to turn brown. Brown leaf tips also may indicate a nutrient deficiency, but in this case, more tissue will turn brown than just the end tips.

Chlorosis and necrosis are two terms which describe symptoms of disease in plants. Chlorosis means lacking green (chlorophyll). Chlorotic marijuana leaves are pale green to yellow or white. Chlorotic leaves often show some recovery after the necessary nutrient is supplied. Necrosis means that the tissue is dead. Dead tissue can be gold, rust, brown, or grey. It is dry and crumbles when squeezed. Necrotic tissue cannot recover.

Symptoms of deficiencies of either N, P, or K have the following in common: all involve some yellowing and necrosis of the lower leaves, and all are accompanied by red/purple colour in stems and petioles. The simplest way to remedy these deficiencies is to fertilise with a complete fertiliser containing nearly equal proportions of three nutrients.

Nitrogen

N is the most common deficiency of Cannabis indoors or out. Nitrogen deficiencies may be quite subtle, particularly outdoors, where the soil may continuously provide a small amount of nitrogen. In this case the opt of the plant will appear healthy, and the plant will grow steadily, but at a slow pace. The deficiency becomes more apparent with growth, as more and more of the lower leaves yellow and fall. The first sign is a gradual, uniform yellowing of the large, lower leaves. Once the leaf yellow, necrotic tips and areas form as the leaves dry to a gold or rust colour. In small pots, the whole plant may appear pale (or lime colour) before many bottom leaves are affected to the point that they yellow or die. Symptoms that accompany N deficiency include red stems and petioles, smaller leaves, slow growth, and a smaller, sparse profile. Usually there is a rapid yellowing and loss of the lower leaves that progresses quickly to the top of the plant unless nitrogen is soon added.

Remedy by fertilising with any soluble N fertiliser or with a complete fertiliser that is high in N. If your diagnosis is correct, some recovery should be visible in three or four days. Pale leaves will regain some colour but not increase in size. New growth will be much more vigorous and new stems and petioles will have normal green colour.

Indoors, you should expect plants to need N fertilisation a few times during growth. Once a plant shows N deficiency, you should fertilise regularly to maintain healthy and vigorous growth. Fertilise at about one-half the concentration recommended for Soilless mixtures. Increase the treatment only if the plants show symptoms again. Once the plants are flowering, you may choose not to fertilise if the plants are vigorous. They will have enough N to complete flowering and you don't want to chance toxifying the soil at this late date.

Phosphorous

P deficiency is not common indoors, but may appear outdoors, particularly in dry, alkaline soils or in depleted soils, or during cool weather. Phosphorus deficiency is characterised by slow and sometimes stunted growth. Leaves overall are smaller and dark green; red colour appears in petioles and stems. The leaves may also develop red or purple colour starting on the veins of the underside of the leaf. Generally the tips of most of the leaf blades on the lower portion of the plant die before the leaves lose colour. Lower leaves slowly turn yellow before they die. Remedy with any soluble P-containing fertiliser. Affected leaves do not show much recovery, but the plant should perk up, and the symptoms do not progress.

Potassium

K deficiencies sometimes show on indoor marijuana plants even when there is apparently enough supplied for normal growth. Often, potassium-deficient marijuana plants are the tallest ((Potassium is associated with apical dominance in some plant species.)) and appear to be the most vigorous. Starting on the large lower leaves, the tips of the blades brown and die. Necrotic areas or spots form on the blades, particularly along the margins. Sometimes the leaves are spattered with chlorotic tissue before necrosis develops, and the leaves look pale or yellow. Symptoms may appear on indoor plants grown in a soil rich in organic material. This may be due to high salinity (Na) of some manures or composts used in the soil. Red stems and petioles accompany potassium deficiencies. K deficiencies that could seriously affect your crop rarely occur with indoor soils. However, mild symptoms are quite common. Usually the plants grow very well except for some necrotic spotting or areas on the older leaves. (This condition is primarily and aesthetic problem, and you may choose not to fertilise. See 19.3.)

K deficiencies can be treated with any fertiliser that contains potassium. Wood ashes dissolved in water are a handy source of potassium. Recovery is slow. New growth will not have the red colour, and leaves will stop spotting after a couple of weeks. In a K-deficient soil, much of the added potassium is absorbed by the soil until a chemical balance is reached. Then additional potassium becomes readily available to the plant.

Calcium

Ca deficiencies are rare and do not occur if you have added any lime compound or wood ash. But calcium is added primarily to regulate soil chemistry and pH. Make sure that you add lime to soil mixtures when adding manures, cottonseed meal, or other acidic bulk fertilisers. An excess of acidic soil additives may create magnesium or iron deficiencies, or very slow, stunted growth. Remedy by adding one teaspoon of dolomitic lime per quart of water until the plants show marked improvement. Periodically fertilise with a complete fertiliser. Foliar feeding is most beneficial until the soil's chemistry reaches a new balance.

Sulfur

S is plentiful in both organic and mineral soils. Liming and good aeration increases S availability. Hence S deficiencies should not occur in soils that are suitable for growing marijuana. However, sulfur deficiencies sometimes can be confused with N deficiencies and may also occur because of an excess of other nutrients in the soil solution. Sulfur-deficiency symptoms usually start at the top of the plant. There is a general yellowing of the new leaves. In pots, the whole plant may lose some green colour. Both sulfur and Mg deficiencies can be treated with the same compound, epsom salts (MgSO4). Epsom salts, or bathing salts are inexpensive and available at drug stores.

Magnesium

Mg deficiencies are fairly common. They frequently occur in Soilless mixtures, since many otherwise all-purpose fertilisers do not contain Mg. Magnesium deficiencies also occur in mixtures that contain very large amounts of Ca or Cl. Symptoms of Mg deficiency occur first on the lower leaves. There is chlorosis of tissue between the veins, which remain green, and starting from the tips the blades die and usually curl upward. Purple colour builds up on stems and petioles.

A plant in a pot may lose much of its colour in a matter of weeks. You may first notice Mg symptoms at the top of the plant. The leaves in the growing shoot are lime-coloured. In extreme cases, all the leaves turn practically white, with green veins. Iron deficiency looks much the same, but a sure indication of Mg deficiency is that a good portion of the leaf blades die and curl. Treat Mg symptoms with one-half teaspoon of epsom salts to each quart of water, and water as usual. The top leaves recover their green colour within four days, and all but the most damaged should recover gradually. Continue to fertilise with epsom salts as needed until the plants are flowering well. If you are using soilless mixtures, include epsom salts regularly with the complete mixture. Because Mg deficiencies may indicate interference from other nutrients, foliar-spray with Mg to check your diagnosis if the plants are not obviously recovering.

Iron

Fe deficiency rarely occurs with indoor mixtures. Iron is naturally plentiful in most soils, and is most likely to be deficient when the soil is very acid or alkaline. Under these conditions, which sometimes occur in moist eastern soil outdoors, the iron becomes insoluble. Remedies include adjusting the Ph before planting; addition of rusty water; or driving a nail into the stem. Commercial Fe preparations are also available. If the soil is acidic, use chelated iron, which is available to the plants under acidic conditions.

Symptoms of iron deficiency are usually distinct. Symptoms appear first on the new growing shoots. The leaves are chlorotic between the veins, which remain dark green and stand out as a green network. To distinguish between Mg and Fe deficiencies, check the lower leaves for symptoms. Iron symptoms are usually most prominent on the growing shoots. Mg deficiencies will also show in the lower leaves. If many of the lower leaves have been spotting or dying, the deficiency is probably Mg. Mg deficiencies are much more common than iron deficiencies in marijuana.

Other Trace Elements

The following deficiencies are quite rare. Trace elements are needed in extremely small amounts, and often enough of them are present as impurities in fertilisers and water to allow normal growth. Many houseplant fertilisers contain trace elements. Trace-element deficiencies are more often caused by an extreme pH than by inadequate quantities in the soil. If a deficiency is suspected, foliar-spray with the trace element to remedy deficiencies. Our experience has been that trace-element deficiencies rarely occur indoors. We advise you not to add trace elements to indoor soils, which usually contain large amounts of trace elements already because of the addition of organic matter and liming compounds. It is easy to create toxic conditions by adding trace elements. Manufacturers also recommend using amounts of trace elements that may be too high for indoor gardens; so use them at about one-fourth of the manufacturer's recommended dose if an addition is found to be necessary.

Manganese

Mn deficiency appears as chlorotic and the necrotic spots of leaf tissue between the veins. They generally appear on the younger leaves, although spots may appear over the whole plant. Manganese deficiencies are not common. Manganese is present in many all-purpose fertilisers. Mn deficiencies may occur if large amounts of Mg are present.

Boron

B deficiency may occasionally occur in outdoor soils. The symptoms appear first at the growing shoots, which die and turn brown or grey. The shoots may appear "burned," and if the condition occurs indoors, you might think the lights have burned the plant. A sure sign of boron deficiency is that, once the growing tip dies, the lateral buds will start to grow but will also die. B deficiency can be corrected by application of boric acid, which is sold as an eyewash in any drugstore. Use one-fourth teaspoon per quart of water. Recovery occurs in a few days with healthy growth of new shoots.

Molybdenum

Mb deficiency occurs in outdoor soils, but rarely indoors. Mb is readily available at neutral or alkaline pH. Mb is essential for nitrogen metabolism in the plant, and symptoms can be masked for a while when N fertilisers are being used. Usually there is a yellowing of the leaves at the middle of the plant. Fertilising with nitrogen may remedy some of the yellowing. However, Mb symptoms generally progress to the growing shoots and new leaves often are distorted or twisted. Mb is included in many all-purpose fertilisers.

Zinc

Zn-deficiency symptoms include chlorosis of leaf tissue between the veins. Chlorosis or white areas start at the leaf margins and tips. More definite symptoms are very small, new leaves which may also be twisted or curled radially. Zn deficiencies may occur in alkaline western soils. Galvanised nails can be buried or pushed into the stem. Commercial preparations of zinc are also available.

Copper

Cu deficiencies are rare; be careful not to confuse their symptoms with the symptoms of overfertilisation. The symptoms appear first on the younger leaves, which become necrotic at the tips and margins. Leaves will appear somewhat limp, and in extreme cases the whole plant will wilt. Treat by foliar-spraying with a commercial fungicide such as CuSO4.

Soilless Mixtures

Soilless mixtures are an alternative to using large quantities of soil. Their main advantage is complete control over the nutrients that your plants receive. Soilless mixtures are also inexpensive and easy to prepare. They have a near-neutral pH and require no pH adjustment.

Soilless mixtures are made from soil components such as vermiculite, sand, or perlite. Soilless mixtures should be blended in such a way that they hold adequate water, but also drain well and do not become soggy. A good general formula is two parts vermiculite to one part perlite. About 10 percent coarse sand or gravel can be added to give weight and stability to the pots. Instead of vermiculite, you can use Jiffy-Mix, Metro-Mix, Ortho-Mix, Pro-Mix and other commercial soilless mixtures, which are fortified with a small amount of necessary nutrients, including trace elements. You can also substitute coarse sand for perlite.

Potting

It is best to use solid containers with soilless mixtures rather than plastic bags. Grow the plants in one- to three-gallon containers. There won't be much difference in the size of the plants in one-gallon or in three-gallon sizes, but you will have to water a large plant every day in a one-gallon container. (The plants can always by transplanted to a larger container.) The pots must have drainage holes punched in the bottoms. Pot as usual, and add one tablespoon of dolomitic lime or two tablespoons of wood ash to each gallon of mixture.

Germinating

Plants may have problems germinating in soilless mixtures. The top layer of mixture often dries rapidly, and sprouts may die or not germinate. Young seedlings also seem to have difficulty absorbing certain nutrients (notably potassium), even though adequate amounts of nutrients are being added. Since this difficulty may retard growth, it is best to start the plants in small pots with soil. Use eight-ounce paper cups, tin cans, or quart milk containers cut in half. Mix three parts topsoil or potting soil to one part soilless mixture. Fill the starting pots and germinate as usual. When the plants are two to three weeks old, transplant to the soilless mixture. First moisten the soil, and then remove the soil as intact as possible. You might handle the transplant like making castles, by carefully sliding the moist soil out of the pot. Or you can cut away the sides of the container while you place the transplant in the soilless mixture. When watering, make sure you water around the stem to encourage roots to grow into the soilless mixture.

Peat pellets that expand are also good for starting seedling. Plant several seeds in each pellet, and place it in the soilless mixture after the sprouts appear.

Fertilising

Soilless mixtures can be treated with a trace-element solution. We have grown crops with no special addition of trace elements, and the plants completed their lives without showing symptoms of trace-element deficiency. In these cases there were apparently enough trace elements in the lime and the fertilisers that were used to provide the major nutrients. Many all-purpose fertilisers also contain trace elements. However, it is a good idea to treat soilless mixtures with a mild solution of trace elements before planting. Large plants can be treated a second time during the third or fourth month of growth. Do not use trace elements more often unless plants show definite trace-element deficiencies.

Iron is the only trace element that is needed in more than minute quantities. Iron can be supplied by mixing a few brads or nails into the soilless mixture.

Use any soluble fertiliser that is complete, that is, that contains some of each of the major nutrients. Choose one with a formula that is highest in N but contains a good portion of both P and K. For example, Rapid-Gro is 23-19-17 and works well for soilless mixtures.

Table 18 gives a formula that has worked well for us. The figures in it are a guide for estimating the amounts of fertiliser to use. When choosing a fertiliser by means of this chart, use N for a guide. For example, suppose the only fertiliser you can find that has good proportions of the major nutrients as a 20-15-15. Divide 5 (the figure for N in the table) by 20 (the figure for N in the fertiliser), and get the result 1/4. That is, the fertiliser if four times as concentrated in N as you need; so you would use one-fourth the amount of fertiliser shown in Table 18. For instance, during the vegetative stage, you would give the plants one-half to three-fourths of a level teaspoon of fertiliser per gallon of water each time you water.

Table 18 – Guidelines for Fertilizing Soilless Mixtures Growth Stage N P2O5 K20 Amount Seedling 5 3 4 1.5 to 2 tsp/gal Vegetative 5 2 3 2 to 3 tsp/gal Flowering 5 5 3 0.5 tp 1.5 tsp/gal It is also not necessary to fertilise in these ratios. You could use a 10-10-10 fertiliser throughout growth; you would use half the amounts listed in Table 18. The most important point is that the plant receive enough of each element, not that they receive specific proportions.

Fertilising according to volume of fertiliser is not very accurate, and also does not take into account other variables (such as variety, light, temperature, etc.) that determine the amounts of nutrients your plants can use. However, it is a simple and useful way of estimating the plant's needs. You can more accurately gauge the plants' needs by giving a sample plant twice the concentration of fertiliser, and another half the concentration. Their performance will give you an idea of whether you are using too much or too little fertiliser. Too much fertiliser is the most damaging condition; so when in doubt give the plants less rather then more. Do not continue to give the plants the recommended amounts of fertiliser if the sample plant that is receiving less nutrients is growing as well as the other plants.

Another way of monitoring the plant's growth is to grow a few plants in a standard soil mixture. This will show you whether the plants in the soilless mixture are growing as fast as they should, and will give you a reference for diagnosing deficiencies.

Besides providing N, P, K, and the trace elements, you must also give your plants secondary nutrients. Ca is added by mixing a tablespoon of lime or two tablespoons of wood ash when preparing the soilless mixture. (Calcium is usually present in water and in many fertilisers as part of the salts that contain nutrients, for example, Ca(NO3)2.) Magnesium and sulfur are both found in common epsom salts, MgSO4. Use one-eighth teaspoon of epsom salts to each teaspoon of 5 percent N. For example, if you are using a 20 percent N fertiliser, you would use half a teaspoon of MgSO4 to each teaspoon of fertiliser. (Actually, enough sulfur is often present, either as part of the soilless mixture or as part of nutrient salts to allow growth.) Magnesium can also be supplied by using dolomitic limestone.

Soilless mixtures are something between soil mixtures and water cultures (hydroponics). With hydroponics, the plants are grown in a tank of water. The fertilisers are added in solution, and the water solution is periodically circulated by a pump.

Another variation on soilless mixtures is to add a small amount of soil or humus to the soilless mixture. Some examples are:

1. 4 parts soilless mixture to 1 part soil; 2. 8 parts soilless mixture to 1 part humus; 3. 15 parts soilless mixture to 1 part limed manure. Overfertilising is less a problem with soilless mixtures then with soil, because of higher concentrations of salts are tolerable in soilless mixtures and because excess salts are easily flushed out of the mixture. A good idea is to flush each pot once after two months of growth, again after four months. Any time the plants show symptoms of overfertilisation, leach the pots immediately. Flood each pot with plain water so that it runs out the drainage holes. Continue flooding the pots until a couple of gallons of water have run through the pot. Don't fertilise for at least a week. Then fertilise with a more dilute solution that was used before. {Figure 51a. Over fertilisation. Leaves turn bright gold and die, starting at the top of the plant.}


Posted – July 1st, 2010
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Pots and Other Containers

In its natural state, marijuana may grow an extensive root system – a fibrous network of fine, lateral roots that branch off a main, carrot-shaped tap root. In dry areas, the tap root can grow more than six feet deep in its search for water. In moist areas with fertile soil (such as in potting mixtures), the lateral roots are able to supply water and nutritive needs and the tap root remains small, often only three or four inches long on a seven-foot-tall mature plant.

The purpose of the growing medium is to provide adequate water and nutrients in addition to anchoring the roots, which hold the plant upright. By watering and fertilising as needed, you could grow a six-foot plant in a four-inch ((Pots are measured by diameter across the top.)) pot or in a three-foot layer of soil over your whole garden; but neither of these extreme procedures is very practical.

Most growers use containers that will hold between two and five gallons of soil. These are a good compromise in terms of weight, space, cost, and labour. They can be moved easily and hold an adequate reservoir of water and nutrients to support a large mature plant.

Some growers use a single large box or several long troughs that hold a six- to 12-inch layer of soil. These have the advantage of minimal restriction of roots and less frequent waterings, but they require more soil and make rotating or moving the plants impractical.

Determine the right size pot to use in your garden by the amount of light per square foot. For a moderately lighted garden (15 to 25 watts per square foot and most window gardens), use one- to three-gallon containers. For gardens with more light energy – over 25 watts per square foot or one-half day or more of sunlight – use three- to eight-gallon containers. The smallest pot we recommend for a full-grown plant is eight inches or one gallon. This is also a good size for starting plants to be transplanted after two months.

Practically any container that can withstand repeated waterings and has a top at least as wide as its base will do. Each pot must have several holes in the bottom to assure drainage. Growers use flower pots, institutional-sized cans and plastic buckets, baskets and small trash cans, milk crates and wooden boxes.

Plastic trash bags are sometimes used when other large containers can't be found. They must be handled carefully, since shifting the soil damages the fragile lateral roots. They are also more difficult to work with when transplanting. However, a roll of trash bags is an available and inexpensive substitute for other large containers. Plastic bags should be double or triple bagged. Small holes should be punched in the bottom to drain excess water. Use masking tape to patch any unwanted tears. The capacity of the bag should be no more than twice as many gallons as the amount of soil used. For example, with four gallons of soil, the bag should be of a five-gallon, but not more than eight-gallon size. Otherwise, it will not form a cylinder, and the bag will remain a shapeless mass.

Use as many pots as can fit in the lighted area to make the most efficient use of space. Many growers prefer to start the plants in smaller pots, transplanting into larger pots when the plants are larger. There are definite advantages to this method in terms of the yield in the garden, given its space and light energy. Seedlings and small plants take up much les space than they will at maturity, so they can be placed closer together. As the plants grow and begin to crowd each other, remove the less vigorous (to smoke, of course) and transplant the rest into larger pots. Start plants which will be transplanted later in four- to eight-inch flower pots, or one-quart to one-gallon tin cans or milk containers. Peat pots or planting pots are made of compressed plant fibre for the purpose of starting young plants. They are available at garden shops and come in several sizes. Use at least a four-inch pot so that the roots are not restricted in early growth. Peat pots are supposed to break down in the soil, but marijuana's delicate lateral roots may not be able to penetrate unless you score or break away the sides while transplanting. Wax paper cup (six to eight ounces), filled with a soil mixture, work as well as peat pots and are cheaper.

BOX C Finding Large Containers Use your ingenuity in finding large containers. Large clay flower pots do not work any better than the large metal and plastic containers discarded by restaurants and food stores. Various milk containers are good starting pots. Many garden shops sell used pots for a few cents each. Wholesalers sell plastic pots by the carton at a discount. Large plastic pots and pails can sometimes be picked up inexpensively at flea markets or variety stores. Any vessel that holds an adequate amount of soil and does not disintegrate from repeated waterings is a satisfactory container.

Properties of Soil

The soil or growing medium serves as a source and reservoir for water, air, and nutrients, and to anchor the roots. Since marijuana grows extremely fast, it has higher water and nutritive needs than most plants grown indoors. The success of your garden depends on supplying the plant with a medium that meets its needs without creating toxic conditions in the process.

There is no such thing as the perfect soil for Cannabis. Each variety can grow within a range of soil conditions. For healthy, full, growth, marijuana prefers a medium with good drainage, high in available nutrients, and near a neutral pH (7.0). These conditions result from a complex set of physical, chemical and biological factors. We will refer to them simply as: (1) texture; (2) nutrients; (3) pH.

Most indoor growers prepare the growing medium using commercial potting mixes. These mixes are usually sterilised or pasteurised and have good general soil properties. Since they seldom list the contents, nutrients, or pH, do some simple test of your basic soil whether you buy or dig for it. Then you can adjust the soil to meet the basic requirements of the plant.

Texture

The texture of the medium determines its water-holding and draining properties. Marijuana must have a well-drained medium for healthy growth. Soils that hold too much water or hold it unevenly can drown the roots, leading to poor growth or death of the plant. In a well-drained soil the roots are in contact with air as well as water. Soils that have too much clay, or are overly rich in compost or other organic matter, tend to hold too much water and not enough air. This condition worsens in time. This is especially true of the soil in pots.

You can determine the texture of your soil from its appearance and feel. Dry soil should never cake or form crusts. Dry or slightly moist soil that feels light-weight, airy, or spongy when squeezed, and has a lot of fibrous material, will hold a lot of water. Mix it with materials which decrease its water-holding capacity, such as sand, perlite, or even kitty litter.

Wet soil should remain spongy or loose and never sticky. A wetted ball of soil should crumble or separate easily when poked.

Soil that feels heavy and looks dense with fine particulate matter, or is sandy or gritty, will benefit by being loosened and lightened with fibrous materials such as vermiculite, Jiffy Mix, or sometimes sphagnum moss.

Soil Conditioners to Improve Texture

Perlite (expanded sand or volcanic glass) is a practically weightless horticultural substitute for sand. Sand and perlite contribute no nutrients of their own and are near neutral in pH. They hold water, air, and nutrients from the medium on their irregular surfaces and are particularly good at aerating the soil.

Vermiculture (a micaceous material) and sphagnum moss contribute small amounts of their own nutrients and are near neutral in pH. They hold water, air, and nutrients in their fibre and improve the texture of sandy or fast-draining soils. Jiffy Mix, Ortho Mix, or similar mixes are made of ground vermiculite and sphagnum moss, and are fortified with a small amount of all the necessary nutrients. They are available at neutral pH, are good soil conditioners, and are also useful for germinating seeds.

Sphagnum and Peat Moss (certain fibrous plant matter) are sometimes used by growers to improve water holding and texture. Both work well in small amounts (10 to 15 percent of soil mixture). In excess, they tend to make the medium too acidic after a few months of watering. Use vermiculite or Jiffy Mix in preference to sphagnum or peat moss.

Nutrients

Nutrients are essential minerals necessary for plant growth. The major nutrients are nitrogen (N), phosphorus (P), and potassium (K), which correspond to the three numbers, in that order, the appear on fertiliser and manure packages, and that give the percentage of each nutrient in the mix (see section 9).

Marijuana prefers a medium that is high in nitrogen, and mid-range in phosphorus and potassium. Generally, the darker the soil, the more available nutrients it contains. Commercial soils usually contain a good balance of all nutrients and will support healthy growth for a month or two, even in smaller (one gallon) containers. Many growers prefer to enrich their soil by adding sterilised manures, composts, or humus. All of these provide a good balance of the three major nutrients. They also retain water in their fibre. In excess they cause drainage problems, make the medium too acidic, and attract insects and other pests. A good mixture is one part compost or manure to five to eight parts of soil medium. In large pots (four or five gallons), these mixtures might provide all the nutrients the plant will ever need. {Table 13.}

The many prepared organic and chemical fertilisers that can be mixed with the soil vary considerably in available nutrients and concentrations. Used in small amounts, they do not appreciably effect the soil texture. Many prepared fertilisers are deficient in one or more of the major nutrients (see Table 14). Mix them together so there is some of each nutrient, or use them with manures, which are complete (contain some of all three major nutrients). When adding fertilisers, remember that organic materials break down at different rates. It is better to use combinations which complement each other, such as poultry manure and cow manure, than to use either fertiliser alone. (See Table 22 in section 13 for a complete list of organic fertilisers.

Table 14 – Prepared Organic Fertilisers Type of Percentage by weight of Availability to fertiliser N P2O5 K20 Plant —————————————————————– Blood meal 13 0 0 Rapid/medium Bone meal 0.5 15 0 Medium/slow Blood/bone meal 6 7 0 Medium/slow Cottonseed meal 6 2 1 Slow/medium Fish meal 8 2 0 Slow/medium Hoof and bone meal 10 2 0 Slow Rock phosphate 6 24 0 Slow Wood ash 0 1.5 3-7 Rapid Greensand 0 0 2-8 Medium/slow Chemical fertilisers are made in about every conceivable combination and concentration. Pick one that is complete and where the first number (N) is at least equal if not higher than both P and K. For example, rose foods may be 12-12-12 or 20-20-20, and work very well for marijuana. Others are: Vigoro 18-4-5 and Ortho 12-6-6. The higher the number, the more concentrated the mix is, and consequently, the more nutrients are available.

Don't use fertilisers which come in pellets or capsules, or that are labelled "timed" or "slow release." They do not work as well indoors as do standard organic and chemical fertilisers. Chemical fertilisers seldom list the amount to mix per pot. You can get some idea by the instructions for application per square foot. Use that amount of each one-half cubic foot of soil mixture.

Many growers add no nutrients at this time but rely on watering with soluble fertilisers when they water. These fertilisers and their application are discussed in section 9.

pH

The pH is a convenient measure of the acidity or alkalinity of the soil medium. It is another way of expressing whether the soil is bitter (alkaline) or sour (acid). The pH is measured on a scale of 0 to 14, with 7.0 assigned neutral; below 7.0 is acid and above is alkaline.

You can think of the pH as a measure of the overall chemical charge of the medium. It affects whether nutrients dissolve to forms available to the plant or to forms the plant can't absorb, remaining locked in the soil medium.

Marijuana responds best to a neutral (7.0 pH) medium, although in a fertile, well-drained soil, it will grow well in a range of 6.0 to 8.5. The simplest way to check the pH is with a soil-test kit from a garden shop or nursery. Test kits are chemicals or treated papers – for example, litmus papers or Nitrazine tape – that change colour when mixed with a wet soil sample. The colour is then matched to a colour chart listing the corresponding pH. Nitrazine tape is available, inexpensively, in drug stores. Some meters measure pH, but these are expensive. Agricultural agents, agricultural schools, and local offices of Cooperative Extension will test a soil sample for pH and nutrient content. Occasionally, a garden-shop person will check pH for you or will know the pH of the soils they sell.

Highly alkaline soils are characteristically poor soils that form cakes, crusts, and hardpan. Soil manufacturers don't use them, nor should they be dug for indoor gardens. Alkaline soils are treated with sulphur compounds (e.g., iron sulphate) to lower the pH.

We have never seen commercial soils that were too alkaline for healthy growth, but they are sometimes too acidic. The pH of acid soil is raised by adding lime (calcium-containing) compounds. Liming compounds come in many forms and grades. Some are hydrated lime, limestone, marl, or oyster shells, graded by their particle size or fineness. Use the finest grade available, since it will have more of a neutralising potential than a coarse grade. You need to use less and are more interested in immediate results than long-term soil improvement. For indoor gardens, use hydrated lime (available in any hardware store) or wood ashes to raise the pH. Hydrated lime is rated over 90 percent for its neutralising potential. Wood ashes will neutralise soil acids roughly one-half as well as hydrated lime. However, they also contain some nutrients (potassium, phosphorus, magnesium, and micronutrients) and are handy and free.

There is no exact formula we can give you for raising the pH. The pH does not have to be exact; it's and approximation. At low pH it takes less lime to raise the pH one point than it does when the pH is near neutral. Sandy soils need less lime to raise the pH one point than soils high in clay or organic matter. In general, add three cups of hydrated lime or six cups of fine wood ash to every bag (50 pounds or a cubic foot) of soil to raise the pH one point. For soils that test slightly acid (about 6.5), add two cups of lime or four cups of wood ash.

Soil that tested below 6.0 should be retested in about two weeks, after thoroughly mixing and wetting the soil. Repeat the application until the pH is in an acceptable range. Check the pH of plain water to see if it is influencing the tests. Distilled water is neutral, but tap water sometimes has minerals that can change the pH. Hard water is alkaline. Sulphurous water and highly chlorinated water are acidic.

If you have already added lime to a soil that now tests from 6.5 to 7.0, don't add more lime trying to reach exactly 7.0. Too much lime will interfere with nutrient uptake, notably of potassium, phosphorus, and magnesium.

General Soil Characteristics

The texture, pH, and available nutrients of the soil are all related. The most important single factor is texture (good drainage). When soil drains poorly, it creates anaerobic (without air) pockets in the soil. Bacteria or microbes that live without air will begin to multiply and displace beneficial microbes that need air to survive. The anaerobic microbes break down organic matter to a finer consistency, and release CO2 and organic acids to the medium. Drainage worsens, the acids lower the pH, and nutrients, even though present, become unavailable to the plant.

The result can be a four-month-old marijuana plant that is only three inches tall, especially if you use high concentrations of manures and composts, peat and sphagnum moss. If your soil lists manures or composts as additives, add no more than 10 percent of these on your own.f

Drainage problems sometimes develop after several months of healthy growth. It is a good idea to add about 20 percent sand or perlite to even a well-drained soil. You can never add too much of these; they con only improve drainage. They dilute the nutritive value of the soil, but you can always water with soluble fertilisers.

Mixtures using many components in combination seem to work particularly well. This may be because, at a micro-level each component presents a slightly different set of physical, chemical and biological factors. What the plant can't take up at one point may be readily available at another.

Preparing Commercial Soils and Mixes Garden soils (or loams) and potting mixes are actually two different groups of products, although they are frequently mislabelled. Some companies sell soil in large bags and a potting mixture in smaller bags, while labelling them the same. Soils and potting mixtures are usually manufactured locally, since transportation costs are prohibitive; so they differ in each area.

 

Texture and Nutrients

Soils and loams are usually topsoil blended with humus or compost for use as a top dressing in gardens, for planting large outdoor containers, or for the soil part of a potting mixture. They may have a tendency to compact under indoor conditions and will benefit from the addition of perlite or vermiculite. Soils and loams usually contain a good supply of nutrients and may support a full-grown plant in a large container. Commercial soils that are heavy generally work better than lightweight soils. Heavy soils usually contain topsoil, in which marijuana grows very well. Lightness indicates more fibrous content.

For example of possible soil mixtures, see Box D. pre?

BOX D Examples of Soil Mixtures* 1. 5 parts soil 2. 8 parts soil 2 parts perlite 3 parts sand 1 part cow manure 1/4 part 10-10-10 chemical fertiliser 3. 5 parts soil 4. 4 parts soil 2 parts perlite 1 part sand 2 parts humus 1 part vermiculite 1/2 part cottonseed meal 2 parts humus 1/2 part poultry manure 5. 3 parts soil 6. 6 parts soil 1 part perlite 2 parts perlite 1 part sand 2 parts vermiculite 2 parts Jiffy Mix 1/2 part poultry manure 1/2 part blood/bone meal 1/2 part cow manure 1/2 part wood ash 1 part wood ash *Almost all fertilisers are acidic, and need to be neutralised by lime. For the above mixtures, or any similar ones, mix in one cup of lime for each five pounds of manure, cottonseed meal, or chemical fertiliser in order to adjust the pH.

Potting mixes are intended to support an average-size house plant in a relatively small pot. They are sometimes manufactured entirely from wood and bark fibre, composts, and soil conditioners. These mixes are made to hold a lot of water and slowly release nutrients over a period of time, which is what most house plants require. For marijuana, these mixes seldom contain enough nutrients to support healthy growth for more than a couple of months. (Their N is usually low, P adequate, and K usually very high.) They work best when sand or perlite is added to improve drainage, and fertilisers are added to offset their low nutrient content.

The pH

Most commercial mixes and soils are between 6.0 and 7.0 in pH, a healthy range for marijuana. If you buy your soil, it will not be too alkaline for healthy growth, but it might be too acidic. You can minimise the chances of getting and acid soil by avoiding soils with "peat" or "sphagnum" in their names. Avoid soils that are prescribed for acid-loving plants such as African violets or azaleas, or for use in terrariums. With common sense, you can buy a soil, add two cups of lime to each large bag, and not have to worry about the pH. However, the surest procedure is to test the pH yourself.

Probably the best way to find the right soil for your garden is to ask long-term growers. They can relate their past experiences with various mixes and blends. Most long-term growers with whom we have talked have tried many of the mixes available in their areas. A reliable, enlightened nurseryperson or plant-shop operator may also be able to give you some advice.

 

Buying Soil Components

 

 

All the materials discussed here are available at farm and garden stores or nurseries. Many suburban supermarkets sell large bags of soil and humus. Always buy your materials in the largest units possible to reduce the cost.

Large bags of soil and humus come in either 50-pound bags or one- to four-cubic-foot bags. A 50-pound bag fills about six gallons. There are eight gallons to a cubic foot. Perlite is sold in four-cubic-foot bags (thirty-two gallons). Jiffy Mix and vermiculite are sold in four-cubic-foot bags and in 16 pound bags (about 18 gallons). Sand, perlite and vermiculite come in coarse, medium, and fine grades. All grades work well, but if you have a choice, choose coarse. Sand (not beach sand) is an excellent soil conditioner. The only disadvantage is its heavy weight. Buy sand from lumber yards or hardware stores where it is sold for cement work. It will cost from 1/50 to one-half the cost of garden or horticultural sand. Sand from piles at construction sites works very well.

Calculating the Amount of Soil

The maximum amount of soil mixture for any garden can be found by multiplying the capacity of the largest pot you plan to use by the number of pots that you can fit in the garden. In many cases, the actual amount of the mixture used will be somewhat less. Two illustrations follow.

1. A small garden with a two-tube, eight-foot fixture (160W). Using 20 watts per square foot for fast growth gives 160W divided by 20W/sq.ft. + eight sq.ft. The largest pot needed for this system is three gallons, but two gallons would work. You can fit about 10 three gallon pots in eight square feet; so 3 * 10 + 30 gallons of soil mixture are needed (see Box E).

BOX E Examples Showing How Much Soil Material to Buy to Fill a Known Number of Unit-Volume Containers Example 1. For a garden eight square feet in size, Buy Component Which amounts to 3 50-lb (6 gal. ea. ) bags of soil 18 gallons 1 cubic foot of perlite 8 gallons 30 lbs of humus 3 gallons 10 lbs of chicken manure 2 gallons TOTAL 31 gallons Example 2. For a garden 24 square feet in size, Buy Component Which amounts to 4 1-cu. ft. bags of soil 32 gallons 2 1-cu. ft. bags of perlite 16 gallons 1 1-cu. ft. bag of vermiculite 8 gallons 20 pounds of cow manure 3 gallons cottonseed meal 2 gallons wood ash 2 gallons TOTAL 63 gallons 2. A large garden with two two-tube, eight-foot VHO fixtures (four times 215 watts or 860 total watts) illuminating a garden three by eight feet, or 24 square feet.

860 watts divided by 24 sq. ft. = about 36W/sq. ft.

The largest pot size for this system is about five gallons. About 16 five-gallon containers can fit in 24 square feet; so 16 * 5 + 80 gal. of mixture are needed. But you could start many more plants in smaller containers and transplant when they are root-bound. You do not use more soil by starting in smaller pots, since all soil is reused. In many cases, you actually use much less soil.

In this system you could start and fit about 40 plants in one-gallon pots in 24 square feet. When the plants begin to crowd each other, some are harvested, making room fir the others, which are transplanted to larger pots. In practice, a high-energy system such as this one (36W/sq. ft.) will grow large plants whose size is limited mainly by the space available. Twelve large female plants are about the most you would want in the system during flowering and for final harvest. Sixty gallons of mixture is all that is needed for the seedlings and the mature crop. This is one-fourth les than the original estimate of 80 gallons, and you actually will harvest a lot more grass (see Box E).

Mixing and Potting

Mix your soil in a large basin, barrel, or bathtub. Individual pots are filled with mixtures by using a smaller container to measure out by part or volume.

Perlite, sand, and dry soil can give off clouds of dust. When mixing large amounts of these, wear a breathing mask or handkerchief over your nose and mouth.

To pot any of the mixtures, first cover any large drainage holes with a square of window screen or newspaper to prevent the mixture from running out. Place a layer of sand, perlite, or gravel about one inch deep to insure drainage. Fill the pots with soil mixture to within three-fourths of an inch from the top of the pot. If your mixture contains manures or composts, cover the last inch or two in each pot with the mixture minus the manure and compost. This will prevent flies, gnats, moulds, and other pests from being attracted to the garden. Press spongy soils firmly (not tightly) to allow for more soil in each pot; otherwise, after a period of watering, the soil will settle and the pot will no longer be full.

Some growers add a few brads or nails to each pot to supply the plant with iron, one of the necessary nutrients. Water the pots and allow them to stand for a day or two before planting. As the soil becomes evenly moist, beneficial bacteria begin to grow and nutrients start to dissolve. {Figure 40.}

Digging Soil

Most growers prefer to buy their soil, while some prefer to dig it. Marijuana cannot tolerate heavy clays, mucks, or soils that dry to crusts. Choose a soil from a healthy garden or field, or from an area that supports a lush growth of annual weeds.

Fields that support a good crop of alfalfa, corn or other grains will support a good crop of marijuana. Fields with beets, carrots, and sugar cane indicate a well-drained soil, with near neutral pH. Red clover, sweet clover, and bluegrass have soil requirements similar to those of marijuana. Garden soils are usually fertile and well-drained, but often need lime to counteract soil acidity.

Take the topsoil layer that starts about two inches below the surface debris. Good soil will look dark, feel moist, and small clean and earthy. Use all of the topsoil layer that maintains its dark colour and is interlaced with roots. Your hands should be able to easily penetrate the underlying topsoil if the soil is in good condition. When the soil changes colour, or roots no longer apparent, then you are past the fertile topsoil layer. Abundant worm, millipedes, and other small lifeforms are a good indication that the soil is healthy. A rich layer of topsoil collects by walls, fences, and hedges where leaves and debris collect and decay to a rich humus. Sift the soil to remove stones and root clods. Also, shake out the root clods, which are rich in nutrients.

Soil that is dug should be tested the same way as already prescribed. It should be adjusted with at least 30 percent sand or perlite (vermiculite for very sandy soils), since potting will affect the drainage of even well-drained soils. Never use manures or composts that are not completely degraded to a clean-smelling humus.

Soil that is dug must be sterilised to kill weed seeds, insect eggs, and harmful moulds and fungi. Some chemical treatments (e.g. formaldehyde) are mixed with water and poured over the soil to sterilise it. Soil can be sterilised in a pressure cooker at 15 pounds pressure for 15 minutes, or by baking wet soil in a large pot at 200 degrees for 30 to 40 minutes. Be advised that baking soil will release some formidable odours.

Growing Methods As we said before, there are probably as many growing methods as there are marijuana growers. These methods are personal preferences or adaptions to fit particular situations; one method is not necessarily better than any other. However, the value of a garden is often based on the amount of high-quality grass it yields. Since indoor gardens are limited in size, you want the plants to quickly fill the garden with lush growth in order to use the garden efficiently. Otherwise, for the first couple of months, the lights are shining on empty space.

 

Secondly, the possession of small quantities of marijuana will probably be decriminalised nationally within the next few years. Decriminalisation for personal possession will open the way for decriminalisation for cultivation for personal possession. But small quantities are more difficult to define for cultivation than for simple possession, which is done by weight. Several possible ways to limit the amount for cultivation have been raised: by the number of plants, by the area cultivated, or by the number of plants at a particular stage of development. The outcome may determine whether you try to grow the largest plants possible or the most plants possible in a given area.

There are several ways to increase your garden's yield.

1. Pinch or cut back the growing shoots when the plants are young. This forces each plant to develop several strong growing shoots and generally yield large robust plants. 2. Plant a number of plant in each pot. 3. Start many plants in small pots and transplant the best plants to larger pots when the plants crowd each other. 4. Use different light systems to grow plants at different growth stages. Here are some examples of how to carry out each of these four methods.

1. Fill the growing area with large containers (about five gallons each). Start several plants in each pot but thin the seedlings over a period of six weeks to two months, until one plant is left in each pot. During the fourth or fifth week of growth, pinch back the plants to about equal heights. Cut the growing shoot at about the fourth internode. Each plant will develop a sturdy stem which will support four to eight growing stems and will quickly fill any empty space in the garden. The whole garden is the treated like a hedge. After another month or two, you cut back the growing shoots again to have plants of equal heights. Remove the male plants as soon as they begin to release pollen (or before any male flowers open for sinsemilla). This will leave more space and light for the females to develop. By the time females flower, they've been cut back two or three times or more, and form a dense growth of growing shoots that fill the garden with a cubic layer of flowers. Some growers maintain the plants for up to a year before the final harvest.

{Figure 41. Plant clipped at fourth internode.}

2. This method also requires large pots. Instead of thinning the seedlings to leave one per pot, leave at least three. After a few months of growth, remove any plants that lag far behind or any plants that show male flowers. The value of this method is that the odds are at least seven to one that any pot will have at least one female plant.

Most of the plants you'll grow will fill out with branches by four months at the latest. Often the branches develop young seedlings. The plants may begin to look like small Christmas trees by the second to third months of growth.

Generally, you don't want to have more than three or four plants in a five-gallon container, because growth will be limited by competition for light and space.

{Figure 42. Basement growing factory in Atlanta.}

Some varieties never do fill out. The branches remain small, only two to three inches long, and yield very little grass. We've seen plants like this grown from grass from Vietnam, Thailand, Afghanistan, and Africa. These plants are also quite short, being four to six feet tall fully grown. With varieties like this, it is better not to pinch tops, and to start about six plants per square foot of garden space. At harvest, the garden will be crowded with top stems that are laden with flower clusters.

Of course, you don't know what varieties will look like until you've seen them grow. For most varieties, each plant will need at least one square foot or space at maturity. It is much less common to find varieties that naturally grow small or especially thin, and, therefore, are those of which you would want to plant more than a few per large pot.

3. Another popular way to grow is to start plants in a large number of small pots. As the plants crowd each other, some are removed and the rest transplanted to larger pots.

4. To get the most for your investment requires conservation of light and soil. When the plants are young, a large number fit into a small place. Some growers take advantage of this fact by having several light systems, each with plants at different growth stages. The plants are rotated into larger gardens and pots. This method conserves space, materials, and electricity, and yields a harvest every two months. Using this method, "growing factories" turn out a steady supply of potent grass. {Table 15.}


 
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What are the Benefits of Aerated Compost Teas vs. Classic Teas?

Aerated compost teas are the latest in scientific organic research today. In many ways, aerated teas offer greater immediate benefits than classic compost, manure, or other homemade foliar teas. Just by applying a cheap aquarium air pump to a 5 gallon bucket of tea, you can get amazing results. (Cheap, inexpensive aquarium airstones are also recommended to be applied to the hose in the water. This produces a better distribution of smaller air bubbles to make the aerobic soil/comosting microbes breed better.) Instead of just brewing teas for quick valuable water soluble nutrients from the compost or manure, you can breed a larger population of beneficial aerobic bacteria and fungi in the tea. It is the microherd in our soil, compost, and teas, that is really more important in soil development and disease control than just the soluble nutrients. Aerobic microherd populations reduce offensive smells in compost piles, the compost teas, and the soil. Aerobic microherd also break down bad poisons and pathogens into safe nutrients in hot compost piles and aerated compost teas. Diluted anaerobic compost or manure teas are great liquid fertilizers and disease controllers also. Many people prefer the anaerobic teas better because they are simpler and easier to design and apply. However, recent research has proven that the aerobic microherd populations fight diseases and bad soil and plant pathogens better and supply more power to your soil's total health and texture. Keep in mind that all types of organic and natural foliar teas are designed to complement and enhance, not replace, basic composting, green manuring, and organic mulching techinques in your garden. The soil microherd continue over months and years to eat up insoluble OM in the existing soil and the extra soil amendments and break them down into more available soluble nutrients for plants later in the year.

Technically even in un-aerated teas there is still some aerobic action taking place for several days. All fungi is aerobic. Some bacteria are totally aerobic, some bacteria are totally anaerobic, and some bacteria can act both aerobic or anerobic based on the soil or tea environment. Un-aerated teas can continue to keep alive some aerobic or aerobic/anaerobic microbes, for up to 10 days in a watery solution. After 10 days, the whole un-aerated tea will contain only anerobic microbes.

You can expect different microbial population levels in your tea based on weather, climate, temperature, seasons, etc. In the summertime you can expect your teas to brew faster and get to your optimal microbial levels faster than in cooler fall weather. Also tea odors, color, and foaminess on top of the tea, will vary based on temperatures too.

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There are several different levels of teas as well as different recipes and styles. Here is the simple steps as outlined by one of our own GardwenWeb members who is an expert on teas and compost. This is a brief description of the different strength levels of tea making as outlined by "BILL_G" :

Level 1: Put a shovel full of good compost in a 5 gallon bucket of water, wait one week, and apply to garden or lawn either full strength or up to a 1:4 water ratio. This is an excellent source of ready available soluble nutrients. NOTE: If you stir your brew daily or every other day, it helps get more oxygen to the mix for better decomposition and better aerobic microbial population growth.

Level 2 : Do same as above, but now add to the recipe a few cups of alfalfa pellets or some other cattle feed. Now you have extra nitrogen and trace elements from the bacterial foods.

Level 3: Do all above plus now add the air pump bubbler. Now you have more aerobic microbes to add to your soluble nutrients in the tea.

Level 4 : Do all the above and now add a few tblsp of molasses or other simple sugar products. Now you really maximize the aerobic microbes in the tea, which in turn produce even more extra soluble nutrients from the bacterial foods.

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Here is my suggestions also. You can add more high nitrogen foods in the tea. Remember the only main ingredients that are necessary to make a good bacterial and soluble nutrients tea are: aerobic compost and sugar products. Everything else is optional. Your teas can be as creative as you are. Let's assume a 5 gallon tea recipe for our example:

1. Add 1/2 bucket of finished hot compost. This supplies most of the beneficial aerobic microbes and soluble nutrients. Some people use slightly immature aerobic compost because it has more fresh nitrogen in it, but less microbes than finished hot compost.

2. Use 2-3 tblsp molasses, brown sugar, or corn syrup. This feeds and breeds the aerobic bacteria. Sugar products are mostly carbon which is what the microherd eat quickly. Add about 1-2 more tblsp of molasses for every 3 days of aerobic brewing to make sure the sugar is digested before touching the soil at application time, and to guarantee that the aerobic bacteria population stays strong throughout the brewing process. Molasses also contains sulfur which is a mild natural fungicide. Molasses is also a great natural deodorizer for fishy teas. For a more fungal tea don't add too much simple sugar or molasses to your aerobic teas. Use more complex sugars, starches and carbohydrates like in seaweed, rotten fruit, soy sauce, or other fungal foods.

3. Add 1-2 cans of mackerel, sardines, or other canned fish. Supplied extra NPK, fish oil for beneficial fungi, calcium from fish bones. Most commercial fish emulsions contain no fish oils and little to no aerobic bacteria. Fresh fish parts can be used, but because of offensive odors, it should composted separately with browns like sawdust first before adding to the tea brew. NOTE: For those organic gardeners who prefer vegetarian soil amendments, you can skip the fishy ingredients, it's not necessary. There is plenty of NPK in alfalfa meal and other grains that you can use.

(NOTE: If you use canned fish products, you may want to let it decompose mixed with some finished compost, good garden soil, etc. in a separate closeable container for a few days before using. Since most canned meat products contain preservatives, this will guarantee that the good microbes in the tea will not be killed off or harmed in brew making.)

4. Add 1 pack fresh seaweed. Supplies all extra trace elements. Seaweed can contain about 60 trace elements and lots of plant growth hormones. Seaweed is a beneficial fungal food source for soil microbes. Liquifying the seaweed makes it dissolve even faster.

5. Add 1-2 cups of alfalfa meal, corn meal, cattle feed, horse feed, catfish or pond fish feed. Supplies extra proteins and bacteria. Corn meal is a natural fungicide and supplies food for beneficial fungi in the soil.

6. Add rotten fruit for extra fungal foods. Add green weeds to supply extra bacterial foods to the tea.

7. Good ole garden soil is an excellent free biostimulant. Garden soil is full of beneficial aerobic bacteria, fungi, and other great microbes. Some people make a great microbial tea just out of soil. Forest soil is usually higher in beneficial fungi than rich garden soil.

8. Fill the rest of the container with rainwater, compost tea, or plain de-chlorinated water to almost the top of bucket. You can make good "rain water" from tap water by adding a little Tang (citrus acid) to the water mix before brewing. Urine water is also an excellent organic nitrogen source for teas (up to 45% N).

9. Some people like to add 1-2 tblsp of apple cider vinegar to add about 30 extra trace minerals and to add the little acidicity that is present in commercial fish emulsions. Many fish emulsions contain up to 5% sulfuric acid to help it preserve on the shelf and add needed sulfur to the soil. You can add extra magnesium and sulfur by adding 1-2 tblsp of Epsom salt to the tea.

10. Apply the air pump to the tea. NOTE: Some organic tea brewers prefer not to use the air pump method. You can get some extra oxygen in the tea by stirring it daily or every other day. The air pump just makes the oxygen levels in the tea happen faster than by hand, thus greatly increasing the rate of aerobic microbial growth in the tea. If you prefer to use the air pump, let it bubble and brew for at least 1-3 days. (NOTE: The 3 days limit is just a good guideline. The real test of brewing time is by your own sight and smell test, because everybody's tea is different due to the various microbial species and breeding activity that takes place during the brewing process.) The aerobic tea is ready to use when it has either an earthy or "yeasty" smell or a foamy layer on top of the tea. If not satisfied with the look or the smell of the tea, go up to a week of brewing. The extra brewing time will help the microbes digest more of the insoluble bacterial and fungal foods in the tea and make it more available for your plant's or your soil's nutritional needs.

Apply this tea full strength to get full nutrient levels per plant, or dilute it from a 1:1 down to a 1:5 water ratio to spread the beneficial microbes over a 1-acre garden area (mix 5 gallons of tea per 25 gallons of rainwater).

To reduce straining, you can place all your ingredients in a closed panty hose or laundry bag during the brewing cycle (don't use a too fine mesh bag or the beneficial fungi can't flow properly through the bag).

Here's another method to avoid straining and to maximize the amount of microbes in application: Simply turn off the air pump, stir the entire mixture real hard, and then let the mixture sit still for about 30 minutes. Scoop off the top juice straight into a watering can for application.

You can apply with a watering can, or simple cup, or in a sprinkling system. All compost teas can be used as a foliar feed or soil drench around plants. They also make great compost pile nitrogen and bacterial activators to heat up the pile for faster finished composting. Always take the remains for teas and recycle them back into your compost piles.

As stated, you can use your homemade tea as a foliar feed or as a soil drench or both. Soil drenches are best for building up the soil microbial activities and supplying lots of beneficial soluble NPK to the plant's root system and the topsoil texture. Foliar feeds are best for quick fixes of trace elements and small portions of other soluble nutrients into the plant through its leaves. Foliar feeds are also good for plant disease control. Foliar feeds work best when used with soil drenches or with lots of organic mulches around plants. You can poke holes in the soil around crop roots with your spade fork, to get more oxygen in the soil to further increase organic matter decomposition and increase microbial activity in the soil.

Aerated teas can also be used to greatly speed up the decomposition process of hot compost piles. The extra aerobic microbes in the tea will breed and cooperate with the aerobic microbes in the organic matter in the compost pile.

You should not use any liquid soaps as a spreader-sticker agent in a fertilizing/biostimulant tea like this. It can hinder or harm your aerobic microbes that you just grew in the tea. You need to use better products in your tea like liquid molasses, dry molasses powder, fish oil, or yucca extract as a spreader-sticker.

A good aerated tea is very economical. 5 gallons can be diluted to biostimulate an entire acre of garden via foliar spraying only. If you soil drench only, it takes at least 15 gallons of tea, before diluting, to cover an acre of garden soil. Also there is enough aerobic bacteria and fungi in a good 5 gallon batch of aerated tea, that is the equivalent of about 10 tons or 40 cubic yards of regular compost!

These homemade aerated compost teas are just as powerful, maybe more powerful, than any commercial natural or organic fertilizer or soil amendment on the market today. And they are a lot cheaper too! So have fun, be creative, and keep on composting!

Happy Gardening!


 
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Many growers think that to be a successful indoor grower you have to go hydro. I would like to present an argument for my organic system.

First of all you should refer to Bushy's Indoor organic tips for beginners in the basic grow room.

All knowledge is practical and has worked well. It is a very simple organic system that is much easier to master quickly than Hydro systems. No meters required, hand watering allowed. This system is cheap and easy to set up but it requires some space, some electricity, and some work.

First the grow room should have at least a 400 watt metal halide light and a few fluorescents for clones and/or seedlings. A 1000 watt MH is preferred depending on the size of your flowering room.

400 watt in the grow room is minimal for a 2500 watt flowering room to stay maximized. Under the 2 or 3 (4 ft. fluorescents start your seeds/clones) keep the growing tips about 1-3 inches max from the light tubes if they are regular 40 watt flor tubes.

I start mine in about 1 Qt pots as seedlings or clones ( I do both) I usually start about 10 every 2 weeks. The perpetual harvest is never all at once, it is more of a production line system, with continual harvesting. As the seedlings reach about 8 inches they are moved into the bigger grow area with the 400 watt metal halide light. Soon they are big enough to transplant into 3-5 gallon pots, depending on size plants desired.

After transplant into big pots the plants need to veg for about another 1-2 weeks until fully or mostly rooted. Rushing this process will hurt eventual yields. I like bigger plants, this is nothing like SOG. If you want to make hundreds of clones and go hydro then SOG is a high yielding system but I like killer larger buds.

The plants spend about 5 weeks in vegetative stage. When moved to the flowering room they are rooted into large pots and usually about 2 feet tall (this varies with your set up, head room, genetics, etc.)

If you have used good soil mix (refer to Basic Tips) and the plant is healthy it should be shooting in fast growth as it goes into flowering. Amazing beautiful bud growth will be seen if all is well. Healthy plants will stay dark green until late in flowering, keep feeding them organic ferts with some Nitrogen in them like Pure Blend or add grow fert to the no Nitro fert if the plant gets yellow.

Make sure you add some co2 to the air twice a day at least in flowering. I water every other day usually and I feed them every other feeding generally. Keep them happy and large yields can be obtained in a 3 month total grow and veg time. 3 oz per plant is not uncommon. Under a 2600 watt flowering room about 24 plants of this size can be grown. This means 4 plants per week to harvest. Ideally it is possible under about a 4k system to grow 10 oz of organic dried bud per week!

It takes work but the product can be unsurpassed! There is nothing about hydro that makes the pot better. So if you are growing for quality but think indoor has to be hydro, think again! BOG is my Advice

——————
BushyOlderGrower


Posted – July 1st, 2010
under CannaLogic
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Maybe you're tired of paying top dollar for weed or you want to make some extra money, but where do you start? This guide assumes you have no prior knowledge whatsoever of growing marijuana. It is not intended to be a complete guide but rather an overview of everything you need to get started. The concept assumes you are growing indoor but some of the concepts can be applied to growing outdoors. If you have ever cared for a house plant you have most of the knowledge you already need to care for a marijuana plant. Marijuana like all plants require these simple things:

*Light
*Food
*Fresh Air

Summary

Marijuana like nearly every other plant starts is started from seed. The plant will sprout out and grow very vigorously to about 2' within 1-2 months. During this time the plant is exposed to 18 hours of light and 6 hours of darkness. This is known as the vegetative state because the plant is concentrating all of its energy into producing leaves, stems and roots. When the plant is about 2' tall the light cycle is changed to 12 hours of light and 12 hours of darkness. This is known as the flowering state because now the plant is concentrating all of its energy into producing buds. This stage lasts 4-12 weeks. After the flowering stage the plant is harvested and dried.

Light

All plants require light and food for a process called photosynthesis. Photosynthesis is the process in green plants by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Photosynthesis release oxygen as a byproduct. Fortunately we only need very modest information about photosynthesis to be successful!

The best type of light for plants is always the sun. The sun is much more powerful than any artificial light. When growing indoors requires we use artificial light rather than the sun but fortunately it has some very important advantages:

*You have a lot more control over lighting cycles and can have multiple crops per year
*Unaffected by different seasons and weather conditions

If you are growing indoor and using artificial light you can never match the actual light output of the sun – therefore you want as much light output as possible. Standard incandescent bulbs (most commonly found in house lamps) are too inefficient at converting electricity into light output for growing cannabis. Although marijuana can be growing using fluorescent lights for best results a HID (High Intensity Discharge) lighting system is highly recommended. There is two types of HID lighting systems are are suitable for growth: HPS (High Pressure Sodium) and MH (Metal Halide). HPS systems are more efficient for the flowering stage and MH are more suitable for the vegetative stage.

Food

Marijuana is a very fast and vigorously growing plant (they don't call it 'weed' for nothing). To ensure it is growing at its optimal potential it is important that you supply it with a constant supply of fertilizer. Fertilizer should be added to the plant about 2 weeks after it has sprouted from the seed and applied until 2 weeks before harvest. The last 2 weeks of harvest where only water and no fertilizer is added is called “flushing”. Flushing is done to remove the excess fertilizer from the plant and to improve its quality.

Fertilizer is such that “you get what you pay for”. Using low-cost generic fertilizers is discouraged in favor of using quality fertilizers designed specifically for growing cannabis. The amount and frequency to fertilizer your plant is specific to the individual type of fertilizer you use. Consult the instructions on the label for specific feeding instructions.

Fresh Air

In addition to light and food C02 is required for photosynthesis to take place. Within the air we breathe there is enough C02 for the plant. Plants through the process of photosynthesis use C02 and convert it into oxygen. If the air in the room is not constantly replaced with fresh air the plants will suffocate and not achieve optimum growth. Ventilation will also keep the grow room at the proper temperature (70-80° Fahrenheit) by cooling the room.

To achieve this your grow room must have some sort of ventilation system. Usually this is achieved with an INPUTOUTPUT ventilation channels. The air is moved via one or more fans. Input ventilation channel is fresh air that is usually taken from outside. No smell is transmitted from the input channel because air is being pulled in. Air is expended via the output channel. The output channel will also remove excess smell and heat generated from lights. and

The output must must take into account the odor produced by the plants. Odor is one of the most common ways grow ops get discovered. Fortunately there is several methods for dealing with the expended air. The first method is by deodorizing the air by using either a charcoal filter or ozone generator. It can then be safely vented back outside without raising suspicion of a grow op via odor. The second method is by venting the expended air to either the sewer system (by taking out the toilet) or through the bathroom or oven vents where it will go through the top of the building and up into the atmosphere (hot air rises).


Posted – July 1st, 2010
under CannaLogic
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American marijuana cultivators are the most sophisticated, scientific farmers in the world. In just a few years they have mastered the techniques of breeding, hybridization, sinsemilla cultivation, and curing. They have doubled and redoubled the yield and potency of their crops.

Although the media usually concentrate on outdoor “farmers,” most outdoor growers these days raise only their own stash, or operate in a limited area using a controlled environment — i.e., a grow room. The high cost of marijuana and the risk involved in its cultivation have constantly challenged the cultivator to develop techniques that use space most efficiently. The potential for a high profit has also given growers the incentive and ability to experiment, and nowhere is this more apparent than in the indoor garden.

I have seen the super grow rooms (SGRs), and I believe. These growers have succeeded. SGRs are based on the idea of limiting factors. The plant’s rate of metabolism — and subsequently its growth rate, maturation time and yield — are governed by environmental conditions that are linked together in a chain. Metabolism can proceed no faster than permitted by the five limiting factors: light, heat, water, nutrients, and carbon dioxide.

Super grow rooms meet these necessities, automatically or semiautomatically, by using timers that regulate irrigation, lighting, and CO2 enrichment. Recently I had the pleasure of seeing two automated grow rooms. The first was lit naturally, with supplemental lighting from metal halides. The corrugated sheet-steel roof had been replaced with Filon, a transparent corrugated plastic sheet made especially for greenhouses.

Exec, as he wishes to be called, grows uniform commercial crops which vary according to the season. He has two growing areas: a starting room and a main growing area. His spacious starting room is divided into a germination section, lit by fluorescents, and a seedling section lit by two halides. Seeds are germinated in 4” pots and transplanted 10 days after germination into a 2½ quart container

Exec has designed a planting schedule that matches each plant varieties’ seasonal habits with day length. Here is his planting and control schedule:
In November, Exec starts equatorial seeds. He prefers a Nigerian-Santa Marta hybrid. He repots 10 days after germination, keeping the germination room lit 24 hours a day. The plants are removed to the large growing area about 3 ½ weeks after germination. This area is completely roofed with Filon, and has 10 halides for supplementary light. Total area is 1,000 square feet.

When plants are moved to the large growing area, they are repotted again, this time into 2-gallon containers. The lighting is set at 12 hours, to coincide with natural light. These lights burn only when the sun is out, so that suspicion is not aroused by the lit Filon roof.

To control the flowering period, Exec has strung rows of removable incandescents, each 100-watt light bulb illuminating about 9 square feet. For the next three weeks he turns these lights on for 1 minute (the minimum time on his short-range timer) every 90 minutes. This prevents the plants from starting to flower. Around the middle of January, he turns off the incandescents. A week later he turns the halides down to 10 hours, where they remain until the end of flowering. Exec claims to have had varieties that would not ripen until the light was down to 8 hours.

Around March 1 the new crop is planted. This time he uses either a Southern African-Afghani or Mexican hybrid. These plants are replanted around March 15 and then, around April Fool’s Day, they replace the earlier crop, which is now ready to be harvested. Exec cuts the plants up and hangs them to dry in his starting room, which he now keeps entirely dark. He manicures them only after they are dry. Exec has a busy schedule transplanting the new residents of the growing area into 2-gallon pots. He keeps the halides on for 13-14 hours and then once again he uses his incandescents nightly, this time for two weeks, until about April 15, when he turns the halides down to 11 hours and covers the roof with long shades made from agricultural shading material. He manually opens and shuts the shades, closing them at dusk, as the lights go off, and opening them late in the morning as the lights come on. In late spring he sometimes uses only sunlight during the brightest part of the day.

On May 15 Exec plants another new crop. This time it is definitely an Afghani-Southern African, which flowers at 14-16 hours of light. By June 15 the Southern African-Mexican hybrid is ready, and the Afghani-Southern African plants are placed in the main garden. They are given only a natural-light cycle, and the halides supplement the natural light only on cloudy days. On July 15 they are shaded, to put them into harvest cycle, receiving no more than 14 hours of light. The plants are ready by August 30, and Exec replaces them with a Northern Mexican-Kush cultivar, or sometimes an Afghani-Kush hybrid that he’s planted a month earlier. He uses flashing incandescents until September 30, when he lets the light cycle drop back to day length. The plants are ripe by December 15, a nice bit of Christmas cheer.

Exec gets four crops a year, uses a minimum of electric light, and is able to grow in a large area, arousing few suspicions regarding spinning electric meters.

He uses a propane heater during the cool months. This enriches the air with CO2 while providing heat. At other times he uses CO2 from a tank. During the hot months he uses a ceiling fan and several high-powered window fans, but even so, at times the room gets a little too warm for optimal growth. Cannabis grows fastest when the temperature ranges between the 60s and the 80s. If the temperature gets higher, photosynthesis stops; if it is lower, photosynthesis slows down.

With about 500 plants per crop, Exec has no time to water them. Instead, he has a drip emitter attached to each container, and each day he waters his plants by turning on a valve for a few minutes. First he determines how much water the average plant needs. Then, using a simple formula — amount required ÷ flow per hour x 60 — he arrives at the number of minutes needed for watering. His emitters flow at the rate of one gallon per hour (gph). If the plants require 8 ounces, 8 ± 128 x 60 3.7 minutes. When he is not around to take care of things manually, he estimates the plants’ needs and then sets his short-term timer, which regulates a solenoid valve.
He adds soluble hydroponic nutrients and other fertilizers and minerals to the water solution several times a month.

These plants are only a month old. They are thriving in a near perfect environment, nutrient, water, and CO2.

The second garden I visited, administered by Elf, was lit entirely by halides and sodium vapor lamps. Elf’s area totals about 225 square feet, of which 175 constitute growing space. He cultivates about 80 plants per crop and claims that he can grow five to six crops per year, but works at a more leisurely pace.

Elf too has a separate starting area. He can start a crop every two months, using the germination area for about one month before setting the plants in the main garden. Plants are started in 2½ quart containers; when they’re moved, he transplants them to 1½ gallon containers.

Sometimes he starts from clones, which takes longer than starting from seeds, but is ultimately less effort since there are no males to deal with. Three weeks after the plants enter the main growing area, its light cycle is reduced to 13 or 14 hours from constant light. Six weeks later, the plants are ready to harvest.

Equatorial varieties take longer to mature, but Elf prefers them to the stuff he sells, so he has a growing room for his own stash. It is stocked with exotics.

Elf ventilates his area with two duct fans and open windows (which are covered to seal in light). CO2 is injected into all three rooms from a CO2 tank with a timer.

Elf waters his plants by hand, using a 5-gallon container and a ½ gallon pitcher. This takes less than an hour. At maturity the plants require about 1/2 gallon of water every four to seven days, depending on temperature. This saturates the container and partially fills the tray underneath it. Each container holds a mixture of vermiculite, perlite, Styrofoam, and foam rubber. Plants that are bigger than most receive extra water between irrigations. Smaller plants receive less water. He uses a combination of soluble fertilizers, and contends that his own urine, either fresh or fermented, is the best source of nutrients available. His plants were healthy and had no nutrient deficiencies. But the taste…

Artificial Light

 

Features
 
 
Florescent light is the most effective and efficient source of artificial light readily available to the home grower. Florescent lamps are the long tubes typical of institutional lighting. They require a fixture which contains the lamp sockets and a ballast (transformer) which works on ordinary house current.

 

Tubes and their fixtures come in length from four inches to 12 feet. The most common and suitable are four- and eight-foot lengths. Smaller tubes emit too little light for vigorous growth; longer tubes are unwieldy and hard to find. The growing area must be large enough to accommodate one or more of these fixtures through a height of at least six feet as the plants grow. Fixtures may hold from one to six tubes and may include a reflector, used for directing more light to the plants. Some fixtures are built with holes in the reflectors in order for heat to escape. They are helpful in areas where heat builds up quickly. You can make reflectors with household materials for fixtures not equipped with reflectors. Try to get fixtures that have tubes spaced apart rather than close together. See 5.5 for further suggestions.

The tubes and their appropriate fixtures are available at several different wattage or outputs. Standard or regular output tubes use about 10 watts for each foot of their length – a four-foot tube has about 40 watts and an eight-foot tube about 80 watts.

High Output (HO) tubes use about 50 percent more watts per length than regular output tubes and emit about 40 percent more light. An eight-foot (HO) runs on 112 to 118 watts. Very High Output (VHO) or Super High Output (SHO) tubes emit about two-and-a-half times the light and use nearly three times the electricity (212 to 218 watts per eight-foot tube).

The amount of light you supply and the length of the tube determine the size of the garden. Marijuana will grow with as little as 10 watts per square foot of growing area, but the more light you give the plants, the faster and larger they will grow. We recommend at least 20 watts per square foot. The minimum-size garden contains a four-foot fixture with two 40-watt tubes, which use a total of 80 watts. Dividing total watts by 20 (watts per square foot) gives 80w divided by 20w/sq. ft=four sq.ft. (an area one by four feet). A four-tube (80 watts each) eight-foot fixture would give: 320w divided by 20w/sq. ft. = 16 sq. ft. or an area the length of the tube and about two feet wide.

VHO and HO tubes in practice don't illuminate as wide an area when the plants are young, because the light source is one or two tubes rather than a bank. Once the plants are growing well and the light system is raised higher, they will illuminate a wider area. Figure about 25 w/(ft*ft) for HO and 35 w/(ft*ft (or foot squared)) for VHO to determine garden size. A two-tube, eight-foot VHO fixture will light an area the length of the tube and one-and-a-half feet wide.

The more light you give the plants, the faster they will grow. Near 50w/sq. ft. a point of diminishing returns is reached, and the yield of the garden is then limited by the space the plants have to grow. For maximum use of electricity and space, about 40w/sq. ft. is the highest advisable. Under this much light the growth rate is incredible. More than one grower has said they can hear the plants growing – the leaves rustle as growth changes their position. In our experience, standard-output tubes can work as well as or better than VHO's if four or more eight-food tubes are used in the garden.

The yield of the garden is difficult to compute because of all the variable that determine growth rate. A conservative estimate for a well-run garden is one ounce of grass (pure smoking material) per square foot of garden every six months.

In commercial grass, the seeds and stems actually make up more of the bulk weight than the useable marijuana.

The grass will be of several grades depending on when and what plant part you harvest. The rough breakdown might be 1/3 equal to Mexican regular, 1/3 considered real good smoke, and the rest prime quality. With good technique, the overall yield and the yield of prime quality can be increased several fold.

Sources

When sunlight is refracted by raindrops, the light is separated according to wavelengths with the characteristic colours forming a rainbow. Similarly, the white light of electric lights consists of all the colours of the visible spectrum. Electric lights differ in the amount of light they generate in each of the colour bands. This gives them their characteristic colour tone or degree of whiteness.

Plants appear green because they absorb more light near the ends of the visible spectrum (red and blue) and reflect and transmit more light in the middle of the spectrum (green and yellow). The light energy absorbed is used to fuel photosynthesis. Almost any electric light will produce some growth, but for normal development the plants require a combination of red and blue light.

Sunlight has such a high intensity that it can saturate the plants in the blue and red bands, though most of the sun's energy is in the middle of the spectrum. Artificial lights operate at lower intensities; so the best lights for plant growth emit much of their light in the blue and red bands.

Fluorescent Tubes

Several lighting manufacturers make tubes (gro-tubes) the produce much of their light in the critical red and blue bans. (Plant-gro (GE), Gro-Lux (Sylvania), Agro-Lite (Westinghouse), and gro-lum (Norelco) are examples, and they look purple or pink. Vita-lite and Optima (Duro-test) produce a white light with a natural spectrum very similar to daylight. Duro-test blubs are more expensive than other tubes but they last twice as long. {See spectrum for "The action spectra of chlorosynthesis and photosynthesis compared to that of human vision. Adapted from IES Lighting Handbook237"}

Theoretically, these tubes should work better for growing plants than standard lighting tubes. However, some standard or regular fluorescent tubes used for lighting actually work better for growing plants than more expensive natural-spectrum tubes and gro-tubes specifically manufactured for plant growth. The reason is that regular fluorescent produce more light (lumens), and overall lumen output is more important for growth rate than a specific light spectrum. To compensate for their spectrums, use them in combinations of one "blue" fluorescent to each one or two "red" fluorescent (Box B).

Manufacturers use standardised names such as Daylight and Sofwhite to designate a tube that has a certain degree of whiteness. Each name corresponds to a tube that emits light in a particular combination of colour bands. For example, Cool White emits more blue light than other colours and appears blue-white. By combining tubes that emit more blue light with tubes that emit more red light, the tubes complement each other and produce a more natural spectrum for healthy plant growth. More "red light" than "blue light" sources are needed to foster healthy growth, so use two red tubes to each blue tube.

The best combinations are either Warm White or Soft White (red) tubes used with either Cool White or Daylight (blue) tubes. These four tube types are common, much cheaper, and when used in combination, will give you a better return than any of the more expensive gro-tubes or natural-spectrum tubes. Any hardware store carries these common lighting tubes, and the cost may be less than a dollar each.

Do not use tubes with "deluxe" in their designation. They have a more natural spectrum but emit considerably less light. Preferably, buy "Cool White" since it emits 50 percent more light than "Cool White Deluxe."

Incandescents and Flood Lights

The common screw-in incandescent bulb produces light mainly in the longer wavelengths: far-red, red, orange, and yellow. Higher-wattage bulbs produce a broader spectrum of light than lower-wattage bulbs. Incandescents can be used alone to grow marijuana, but the plants will grow slowly and look scraggly and yellow. Incandescents combined with fluorescent work well, but fluorescent are a better source of red light. Fluorescent tubes generate slightly less heat per watt. With incandescents, heat is concentrated in the small bulb area, rather than the length of the tube, and can burn the plants. In addition, incandescents have less than one-third the efficiency of fluorescent in terms of electricity used. If you decide to use incandescents in combination with fluorescent, use two times the wattage of incandescents to blue source fluorescent, that is, two 40-watt Daylight tubes to about three 60-watt incandescents, evenly spacing the red and blu sources.

The common floodlight has a spectrum similar to but somewhat broader than incandescents. Because they cast their light in one direction and operate at higher intensities, these lights work better than incandescents, both as a single source and to supplement natural or fluorescent light. {Figure 33. Supplement natural light with floodlights. Use foil curtains for reflectors.}

The best application for floodlights and incandescents is to supplement natural and fluorescent light, especially when the plants get larger and during flowering. Incandescents and floodlights require no special fixtures, although reflectors increase the amount of light the plants receive. These lights are easy to hang or place around the sides of any light system, and their strong red band promotes more growth and good flower development. Some of their energy is in the far-red band. Most purple gro-tubes and white fluorescent are deficient in this band, and addition of a few incandescents make them more effective. Agro-lite and W/S Gro-Lux emit adequate far-red light and need no addition of incandescents.

Several companies make screw-in spotlights specifically for plant growth. Two brand names are Duro-Test and Gro n'Sho. Although they are an improvement over incandescents as a single source, these lights don't perform nearly as well as fluorescent. A 150-watt bulb would grow one plant perhaps four feet tall. Two eight-foot fluorescent tubes (160 watts) will easily grow eight six-foot plants. For supplemental lighting, the incandescents and floodlight work as well and are cheaper.

HID Lamps. Metal Halide (MH) and Sodium-Vapour Lamps (HPS)

HID's (High-Intensity-Discharge) are the lamps of choice for serious indoor gardeners. HID lamps commonly illuminate streets, parking lots, and sports stadiums, and they emit very intense light and produce more light, more efficiently than fluorescent. All HID's require specific ballasts and fixtures to operate, so purchase complete systems (fixture, ballast, reflector) along with the lamp. High Times and Sinsemilla Tips magazines (p. 332) feature numerous ads by retailers of horticultural HID systems. Contact the advertisers, and they'll send you brochures with enough information to make an informed choice.

Ordinary metal-halides (MH's and HP's) may emit dangerous UV and particle radiation of the bulb envelop breaks, cracks, or develops a small hole. Broken MH bulbs may continue to operate apparently normally, and exposure may cause serious eye or skin injury. Make sure to purchase MH bulbs designed with a safety feature (such as GE Sat-T-Gard or Sylvania Safeline) that causes the bulb to burn out immediately if the outer envelope ruptures. OR purchase fixtures that shield the bulb in protective tempered glass.

HID's come in many sizes, but generally, use only 400 and 1,000 watt sized lamps. The largest size (1,500 watts) is not recommended because of its relatively short bulb life. Sizes less than 400 watts do not return as much marijuana considering set-up costs and ease of operation. The only exceptions are certain "self-contained" mini-units of 150 and 175 watts (see 4.1). These mini-self-contained units have a horizontal fixture and built-in ballast, which is easy to set up. The horizontal fixture directs up to 45 percent more light to the plants than conventional, vertically positioned lamps with reflectors. The intense light encourages excellent growth and bud formation with modest electrical consumption. They are the best overall light system for small, personal gardens such as closet set-ups.

Position 400 watt HID lamps 18 to 30 inches above plant tops, and 1,000 watt lamps 30 to 42 inches above the tops. During flowering, flowers may "run" rather than form in compact buds if lamps are positioned too close to the plant tops, particularly when using HPS's.

Heat is the main problem with HID's, and the room must be well-ventilated. Use exhaust fans to draw heat out of the room. The fan doesn't need to be large, just active enough to create a strong, ventilating draft.

Light Balancers

Sophisticated gardeners use light balancers which employ a small motor to move reflectors and HID lamps held on tracks or mechanical arms slowly across a garden in either a linear or circular pattern {(see p. 88 Figure 38b)}. Light balances save considerable power and bulb costs because they dramatically increase the effectively illuminated garden size, while using less the 24 watts per balancer. With the lights moving on a balancer, all of the garden becomes equally illuminated for modest running costs. Instead of adding another 1,000 watt HID, a light balancer increases the garden size without measurably increasing power consumption, an important consideration when electricity consumption or costs are of concern.

With multi-bulb HID gardens, use one MH to each HPS lamp on a light balancer, and hang the lamps about one foot closer to the plant tops than usual. MH's favour blue light, and HPS's produce more orange-red light. By combining the two, the spectrum is more balanced, and you'll get a better return of well-formed buds.

Low Cost HID Systems

By far, the most efficient and effective set-up for a modest artificial light garden is to use fluorescent lamps set on a long photoperiod for germination, growing seedlings or to raise clones; use another room,, or part of the room separated by a light-tight curtain or barrier, for flowering with (HPS) lamps in horizontal reflectors kept on a short photoperiod to induce and promote flowering.

For example, separate and average sized room into two growing areas by hanging an opaque curtain to block light between the two sections. In the smaller area, grow seedling or clones (see 18.5) for two to six weeks under fluorescent set on a constant light. In the larger section, keep HPS lamp(s) on a 12-hour light cycle for flowering. Move larger seedlings under the HPS lamp(s) for about 9 to 15 weeks to initiate and complete flowering. Meanwhile, start more seedling under fluorescent. It's easy to maintain both sections of the room be constantly replenishing either area with new plants. This setup is very productive for a modest investment in both costs and labour – no time or costly light and electricity is wasted on empty space, and you'll find yourself continuously harvesting mature buds.

{A no frills setup with an HID. Notice that the ballast is insulated from the floor with pieces of wood; the fixture is supported by rope and not the electric cord; plastic protects the floor; there is a timer, a reflector, and fan.} {Figure 34 and 35 for light-output from two and four 40 watt white fluorescent and comparing effectiveness in footcandles.} Using this setup, the initial long photoperiod and small area necessary for seedlings or clones is illuminated cheaply by fluorescent. Seedlings grow, and cuttings root, better under fluorescent than HPS's. The larger, more costly flowering section is kept under a short photoperiod of 12 hours of daily light and the strong red light is necessary for good flowering.

For example, the whole operation could draw less then 650 watts: 160 watts by four, four-foot fluorescent set on constant light to start the seedlings; one 400 watt HPS set on 12 hours daily light for flowering; two timers and a venting fan for automating the lights and controlling heat. It's possible to harvest four to six, fully mature crops each year, or continuously harvest. (See Mel Frank's new Marijuana Grower's Insider Guide by RED EYE PRESS for much more information on efficient, low cost, indoor systems and greenhouse gardening.)

Setting up the Garden

Under artificial light, marijuana grows from three to sic feet in three months, so the height of the light must be easy to adjust. Fixtures can be hung from the ceiling, shelves, walls, or from a simple frame constructed for the purpose. If you are hanging the lights from the walls or ceiling, screw hooks directly into a stud. Studs are located in every room corner and are spaced 16, 18 or 24 inches apart. Light can be supported from lathing using wingbolts, but plaster is too weak to hold a fixture unless a wooden strip held by several wingbolts is attached to the walls or ceiling first to distribute the pressure. Then hang the fixture from a hook in the strip. Closets have hooks and shelves or clothes rungs that are usually sturdy enough to support the fixture. People have gardens under loft beds.

Chains are the easiest means of raising and lowering fixtures. Two chains can be suspended from a solid support from above, and attached to an "S" hook at each end of the fixture. Raise the fixture by inching the hooks to higher links on the chain. Or tie rope to the fixture, pass through an eye hook or pulley in the ceiling or frame, and tie-off at a hook or boat cleat anchored in the wall or frame.

You can also hang the lights permanently and lower plants on a shelf or plywood. The shelf could be suspended or lowered by supporting the shelf with progressively smaller block. This arrangement is often used in "growing factories" where plants are rotated to larger gardens and grow for only a few weeks in each space. One garden may have fluorescent for starting plants and another garden for maturing plants under HID's. With HID's and skylights, lowering the plants may be your best option. Use lightweight soil components or hydroponics rather than heavier soil, and the operation is easier.

If you plan to use six or more fluorescent, remove end sockets and ballasts from fixtures. Mount end sockets and tubes on a frame of one-by-twos or plywood. Space sockets so tubes cover the garden evenly (see Figure 37 and 38). This arrangement illuminates the garden more evenly and drastically reduces the suspended weight since ballasts make up most of a fixture's weight. Keep ballasts off floors and away from water. Mount the ballasts on a nearby wall or on a wooden box. Wet ballasts could actually explode, and at best, are electrically dangerous when wet.

Always buy fixtures with reflectors. For HID's, companies make their own reflectors, but the best reflectors are for horizontally positioned lights no matter which company. Horizontal reflectors focus much more useable light than either parabolic or cone reflectors. HPS's can work in any position, but MH lamps are made to work in either a horizontal or vertical position, and you must buy bulbs that correspond with the fixtures.

For fluorescents, you can make an overhead reflector from the cardboard cartons in which tubes and fixtures are packaged. Cut off the end flaps and form the cardboard into a "U". Face inner side with aluminium foil or paint them white. Leave enough space so the foil or cardboard does not contact end sockets. Staple or tape the reflector behind the tubes to the fixture or from to reflect light toward the plants.

Surround all garden with reflective surfaces, but not so tightly that air can't freely circulate. Even in window gardens, reflective sheets set adjacent to the plants make a marked difference in growth. When artificial lights are high, reflectors from the floor on up keep lower branches actively growing. Mylar, with its mirror-finish, is popular for facing walls. A flat white paint (super or decorator white) reflects better than glossy white or aluminium foil. Flat white has about three percent more reflecting capacity than aluminium foil, and reflects light more uniformly. The difference is slight, so use whatever means is most convenient. Paint walls that border the garden a flat white or cover them with aluminium, mylar, or white plasterboard. {Figure 36. Reflectors can be made from sturdy paper faced with aluminium foil. Make them with staples, tape, or tacks. Figure 37.}

Natural-light gardens also benefit from reflectors. Make them out of cardboard painted white or faced with aluminium foil. Once the plants are past the seedling stage, surround them with reflectors; otherwise only one side of the plants will be fully illuminated.

Covering the floor with a plastic dropcloth (about $1 at any hardware store) will protect your flor and your neighbour's ceiling from possible water damage.

Marijuana grows well in a dry atmosphere, but heated or air-conditioned homes are sometimes too dry during germination and early growth. Enclosing the garden in reflectors will contain some of the moisture and insure a healthy humidity. White sheet plastic is available to enclose open gardens. Do not completely enclose the garden. Leave some open spaces at the bottom, top and ends of the garden to allow air to circulate. Air circulation will become more important as the plants grow larger.

Don't rely on training your pets to stay out of the garden. The garden will attract them, and they can easily destroy young plants by chewing on leaves and stems. Soil is more natural to their instincts than the sidewalk or kitty litter. Protect the garden from pets and toddlers; surround it with white plastic or chicken wire. Large plants are more sturdy and animals can do them little harm. The jungle ambience and an occasional leaf are irresistible to most cats, and they'll spend hours in the garden.

Electricity

For most growers, the amount of electricity used is of little concern. A four-tube, regular-output, eight-foot fixture draws about 320 watts per hour or about the same as a colour TV. The cost increase to your electric bill will be about two to six dollars a month, depending on local rates.

Farmers who devote entire basements or attics to their gardens are sometime restricted by the amount of current they can draw. Older homes or apartments may have only one 15-ampere circuit but more often have two, for 30 amperes total. Newer homes have either 60 or 100 amperes available through four to six circuits. One 15-ampere circuit can safely accommodate three, two-tube VHO fixtures or six tubes for 1,290 watts, or 16 regular-output, eight-foot tubes for about 1,280 watts total. This allows for a 20 percent safety margin of circuit capacity, which is necessary considering heat loss, starting voltages, etc.

In kitchen and basements the circuits may be rated higher, at either 20 or 30 amperes. You can find out the amperage of the circuit by looking at the fuse rating on the face of the fuse. Determine what room or rooms each circuit is feeding by removing the fuse and seeing which outlets are not working. The wattage capacity of any circuit is found by multiplying volts time amps. Standard United States voltage is 110 to 120 volts.

Fluorescent light fixtures are sometimes sold unwired or without a line cord, and the job is left to you. Follow the diagram on the ballast which shows the wires marked by their colour. Simply attach the wires to the sockets as diagrammed. New sockets have small holes which automatically make contact when the bare end of the wire is pushed into them. Older fixtures have sockets with conventional screw terminals.

Indoor gardens may have aluminium foil, chains, reflectors, and wet floors, all of which are good electrical conductors. Coupled with hanging lights, these conditions could lead to dangerous electrical shocks. Never touch a reflector, fixture, or ballast while watering or standing on a damp floor. Eliminate the chance of serious shocks altogether by turning off the lights whenever you work in the garden. An HID ballast on a damp floor is very dangerous. Raise HID ballasts on wood blocks off the floor.

Reduce the risk of dangerous shocks by using fixtures grounded to the power source. A fixture with a three-pronged plug connected to a three-wire outlet is grounded in a properly wired house. You can also ground a fixture by connecting a #12 or #14 gauge wire to any bare metal screw (not an electric terminal) on the fixture housing to the screw that holds the cover plate on the electrical outlet your using.

{With two prong outlets, connect an adaptor plug with a terminal (top left) or third wire (top right) from the plug to the screw that holds the cover plate. This converts two-wire outlets to three wire grounded systems when a three-wire electric cord is used, an important electrical safeguard which grounds the light system.}