Chapter 15


Marijuana is a fast-growing annual whose survival depends on its ability to compete with other fast-growing weeds. At the end of each season, plants growing in a wild stand may cover the ground with thousands of seeds per square foot. Many of these are relocated by wind, runoff, and birds, and some are destroyed or die. Other never receive the conditions they need to germinate; and of those that do germinate, many die as seedling. The remaining plants compete with each other and with other weeds for the available light, nutrients, and water. Even so, wild stands may be as dense as forty plants per square foot. In order to survive the competition, Cannabis expends a great deal of its energy during the first two month growing a main shoot which is taller than the surrounding vegetation. Then it develops lateral branches which shades the shorter plants. With their source of energy - light - cut off, the shaded plants stop growing and often die.

When you cultivate - that is, eliminate weeds - the rate of germination and survival of your plants is increased enormously. Growers using clover, sheet composting, or mulch as ground cover cane expect very little interference from weeds during seedling development. But plots of fertile, aerated, and cleared soil are open to colonisation by a wide range of plants; so you may have to weed several times before the marijuana's dominance is assured.

When you weed, make sure not to pull out any weed seedlings which may have roots in the same area as the Cannabis roots. Instead, cut the weeds slightly below the surface with a cliperr, scissors, or your fingernails. Weeds more than six inches away can be safely pulled. Leave them to dry right on the soil. As they dry and decay, they return the soil's nutrient to it.

Growers plagued with weeds can cover the soil with mulch, paper, or polyethylene sheets. One grower found that two computer sheets fit exactly between the rows. Another used torn drapes as a temporary ground cover.

Once Cannabis has established dominance over an area, the other weeds are not able to interfere with its growth. But if there is wide spacing between the plants, the weeds may have open space and start to grow rapidly. Keep these weeds clipped short if water or nutrients are scarce.


Marijuana requires an ample supply of water to live and grow. The actual quantities that it needs depend on the plant's size, the gardening techniques, type of soil, temperature, wind, humidity, and intensity of light. A vigorous plant may transpire several gallons of water a day during the hot summer months. If it receives less water then it need, it stops growing, wilts, and then dries out. {Figure 66 Areas with less than 30 inches of rain usually require some irrigation.}


Marijuana germinates best in a moist soil. Within a week, it grows a taproot three or four inches long. By the end of the first month, the root system may stretch over an area a foot and a half in diameter and go more than one foot down. Until then, the soil should not be allowed to dry out. Plants which have germinated during warm, sunny weather may need to be watered until the roots have grown deep enough to reach sub-soil moisture. When the soil three inches below the surface feels dry, seedlings should be watered, preferably by using a watering can or the spray setting on a hose. Gently water the soil, making sure not to disturb the seedlings or the soil surrounding. The soil should be thoroughly saturated so the moisture percolates down, encouraging the roots to grow deep. If the surface is inly lightly watered, the roots may grow near the surface, leading to water problems as the soil gets drier during the summer.

After the first month, Cannabis does best when the soil goes through alternating moist and dry periods. This alternation allows the lateral roots to come into contact with air. By the end of the growing season, the root system may penetrate the soil to a depth of six feet or more. As long as they are not blocked by solid rock or dense clay, the roots grow by following a trail of moisture. If the trail leads deep, the roots follow. The deeper layers of soil are less likely to dry out during hot, dry weather.

Older Plants

As a rule of thumb, Cannabis over a month old should be watered when the soil about six inches deep feels dry. But this rule provides only a rough indication that the plants need water, because there may be deeper sources of water that are not apparent. The most obvious indication of a problem is wilting. A more subtle one is slow growth during the (ordinarily fast-growing) vegetative stage.

Since you want to wet the lower layers, you should thoroughly saturate the soil. If the soil is completely saturated, it should hold water for a minimum of a week. Usually only two or three waterings a month are required by a garden that is completely dependent on irrigation.

The most efficient way to water is to let the water slowly seep into the soil, so that all the organic particles which hold the water are saturated. If the soil is very dry, and the water beads or runs off and is not absorbed, add household laundry detergent at the rate of one or two grams per gallon of water. It acts as a wetting agent, which breaks the surface tension. Once the soil is treated with a wetting agent, it usually absorbs water throughout the growing season.

In drier areas where corn. cotton, and other deep-rooted crops are irrigated, marijuana also requires an additional source of water. But in areas where there are patches of wild hemp or where deep-rooted crops grow by using available ground water, marijuana does not need to be watered, although additional water may increase its growth.

Box I

Water in General

Deep soil layers retain water much longer than the top layers. To encourage the development of a deep root system, saturate the ground when you water. The roots follow the moisture trail.

Water conditions also vary from field to field. For instance, many mid-western farmers plant along the banks of meandering streams. Even in dry areas, these plants have a natural source of water. Mountainous areas are usually well-drained and dry out before valleys do. Low-lying fields remain moist later, and are saturated by runoff from higher ground. In browned areas, farmers look for green spots which indicate underground streams, springs or runoff. Planters look for deserted wells or active watermains with leaks. Fields high in organic matter retain moisture longer than other fields, and mulching may cut water evaporation by 50 percent.

Watering Techniques

Gardeners may supply water by using a bucket, can, or water-hose. But growers with larger plots often rely on waterpumps to deliver river, lake, or well water to their gardens. Irrigation canals, drainage pipes and ditches, and water mains are sometimes convenient sources of water. The two most efficient methods of watering are the drip hose, which seeps water around the plant, and hand watering into an enclosed area around the plant's stem.

There are several kinds of drip hoses. Some have perforations every three to six inches along their length. These are useful when marijuana is planted in rows or large hills. Another kind is actually a kit, consisting of a main feeder hose and several side hoses two to four feet long. Each side hose has a metal bulb at the end which can be adjusted to regulate water flow. The bulb lies near the plant stem. A drip bottle was invented by a grower in the dry area of Nebraska who was only growing a few plants. He punched pinholes in the bottom of several one-gallon milk jugs and placed a jug near each plant. The jugs slowly watered the garden. Every few days, he refilled the jugs from a nearby irrigation ditch. As the plants grew larger, he placed more jugs around them. The drip method moistens the soil slowly, but does not flood it; so the soil and its nutrients are not washed away. Since this method allows you to decide exactly where the water goes you need not waste any on non-productive land.

Growers sometimes use elaborate setups, such as battery-electric, hand- or foot-powered, ram- or windmill-driven pumps. Foot-powered pumps are probably the most convenient for small plots. They are extremely lightweight (just a little heavier than a bicycle), inexpensive, easy to construct and disassemble, and virtually silent. Since you have much more power in your legs than in your arms, foot-powered pumps con do more work, and do it faster, than hand-powered pumps.

Electric pumps are relatively quiet and pump and enormous amount for their small size. But they require a source of electricity. They cannot be used unless there is a power line available, although there are car alternators available which produce 110-volt current.

Gasoline pumps and electric generators are heavy and noisy. Even with a muffler, they can be heard for miles in some country areas. They require a source of fuel, and often an elaborate setup, including rigid feed tubing, fuel tank, and platform. But once they are in place, the can deliver a tremendous amount of water. They are usually used by farmers growing large plots. Sometimes growers dig a hole in which they store and run the equipment. This setup helps muffle the sound and keeps the machinery in good working order.

Ram- and windmill-powered pumps use running-water and wind energy, respectively. They come in many sizes and are often used to fill water tanks for later use. They can also be used to generate electricity to run electric pumps. They require no fuel, are usually silent, and can be constructed inexpensively.

But some farmers have devised other methods for getting water to their plants.

A farmer growing near Tucson, Arizona, trucks water to her plants twice a week using a pickup truck and for 55-gallon barrels. She attaches a garden hose to her tanks, and siphons the water to her garden, 200 feet downhill.

Two foresighted farmers in Texas carried twenty 30-gallon plastic trash cans and lids to their garden. During the spring rains, they filled the containers from nearby gullies. By the end of the rainy season, the had collected enough water to carry them through the summer drought.

A homesteader in Oregon's dry eastern section dammed a gully by using and earth stabiliser, plastic, wood and cement, and pipe. During the winter his private reservoir filled.

Farmers near Atlanta tapped into a city water main. The pressure from the water main allowed them to pipe water uphill.


If the soil is kept moist during germination, most of the viable seeds that you planted will germinate and the seedlings will soon start to crowd each other. This happens frequently when the plants grow on their own. Then they grow into a dense hedge-like mass dominated by a few plant. The dominant plants typically have long internodes and a long sturdy stem with little branching. The shorter, bushier plants are shaded by the taller ones and become stunted from the lack of light. By thinning, you give the plants that are left enough room to grow to their full potential, and you choose the ones that you think will grow to be the best for smoking. Leave the plants that have dense foliage, are branching, and, later in the season, the ones that are the most potent.

Thin the plants as soon as they begin to touch or crowd each other. This should be repeated as often as necessary. Seeds sown six inches apart in rows two feet wide require thinning several times during the season. But guerilla farmers sometimes let the plants compete so that the garden looks more like a wild stand.

There are two methods used to thin: cutting the stem at the base so that the entire plant is destroyed, and cutting just the tops so that the plant's growth is thwarted, and the uncut plants shade it. The cut plants remain relatively inactive, and do not use much water or nutrients, but they do shade the ground and use otherwise wasted space.


Outdoor-grown plants rarely need staking. When the stem bends from the wind or rain, tiny tears in the structure develop. These are quickly mended by the plant: it grows new cells which increase the girth of the stem and make it stronger. But plants which are suffering from nutrient deficiencies pr are top-heavy because of competition may need to be staked. Heavy rain sometimes cause the plants to fall over, especially if they have shallow root systems which cannot hold the added weight.

To stake, drive a sturdy rod six inches from the stem and deep enough into the ground to be able to give the plant support. Then tie the stem to the stake with wirer twists or string.

If the stem or the branch is cracked, pinched, or bent at the base, its position should be corrected and held firmly with a splint. The splint can be held with masking tape. In a few days the plant grows tissue to support the damaged area.


Growers prune (clip or top) their plants to increase productivity, prevent detection, or to harvest early smoke. In the near future, new laws will decriminalise or legalise marijuana cultivation. These laws will probably limit legal cultivation either by the total gardening area or by the number of plants an individual or group may cultivate. Gardeners limited by space will maximise yield by cultivating a dense stand of tall, unclipped marijuana. Growers permitted to grow only a few plants will grow the largest, most productive plants possible. This is done by giving the plants the best possible growing conditions and a lot of space between plants to maximise light and minimise competition for water and nutrients.

Unpruned marijuana develops in one of three classic shapes, depending on variety. Many Mexican and Thai varieties develop into a tall, narrow bush no wider then three feet and shaped like a poplar tree. Colombian, Cambodian, Indian, and some south Mexican and Vietnamese varieties are Christmas-tree shaped. Some Moroccan and Afghani varieties have complex branching and naturally grow into small, dense bushes, about five feet tall. Marijuana usually grows to its full height by early September. Most of the marijuana plants you are likely to cultivate will grow to between eight and fifteen feet tall. Some Hawaiian and Thai varieties average between twelve and twenty feet tall.

Increasing Yield

When marijuana is clipped to increase the number of growing shoots, the total yield at season's end may not be increased. Provided that soil and water are not limiting to growth, each plant can reach a maximum size when given enough room. The more surface are the plant presents to light, the closer it will get to its maximum potential. Where the plants are grown with much space between them, clipped plants can yield more than unclipped plants, especially if the branches are spread out to maximise the light on the plant. When the plants are grown close together, the taller a plant is, the more sunlight it will receive, and hence the larger the possible yield.

Some growers prefer to harvest a top stem that is thick with buds (colas). The largest colas form on the main growing shoot of unclipped plants. When the growing shoot is clipped from a plant, the new shoots and leaves grow slower and smaller than the main shoot of an unpruned plant because the capacity for growth is spread out over several shoots. When a plant is clipped early in the season, most of the difference in lead and bud size is made up by harvest time.

Marijuana can be pruned at any time during the seedling or vegetative growth stage, but you should prune plants when they are young if you plan on harvesting growing shoots during the season. A seedling clipped anywhere from the fourth to sixth node will usually form at least six strong growing shoots that can be harvested during the third or fourth month. If these shoots are cut again while the plant is still young, marijuana often develops into a small, very compact, hedge-like bush.

Yield can be increased by spreading the plant's branches so that more light reaches the inner growth. Cannabis stems are bent most easily when they are still green and fleshy, nearer to the new growth, but the whole plant can be bent to form a gentle arch with the top of the main stem in a horizontal position. Within a few days the side branches along the top will begin to grow vertically, competing with the main stem. They will soon develop their own horizontal side branches. To bend a plant, tie the main stem loosely with a cloth or heavy string. Tie the other end of string to a heavy weight or anchor on the ground. Don't put too much pressure on the stem as this tears some of the roots and weakens the plant. You can bend the plant a little each day until the plant is in the desired position.

You may also increase yield by bending only the growing tip. This encourage the side branches to develop sooner than they naturally would. Only the flexible part (about the last foot) is bent. To bend the top, use stiff wire or wire twists used for plastic bags and wrapping vegetables. Fasten the other end of the wire lower in the stem to hold the tip in position. {(See Figure 49.)}

A common mistake that cultivators make is pulling off the large leaves on the main stem (sun or fan leaves), when the plants are young. These leaves are removed by cultivators who believe that their removal will cause the undeveloped side shoots to grow. But fan leaves are net producers of sugar and energy, which are used by the side soots to begin growth. Rather than encouraging new growth, the removal of fan leaves slows growth. The plant will also be more susceptible to attacks from pests and predators.

When the plant is several weeks old and growing well, the difference between plants with their leaves removed and those left intact may not be large. The biggest difference can be seen when leaves are removed from branches just prior to, or during, flowering. The buds that form from leaf axils with leaves removed are noticeably smaller than those where the leaves have been left on the branch.


Cannabis can be detected from both the ground and the air. From the ground, marijuana is revealed by its familiar shape, unmistakable leaves, and odour. Tall plants are usually more conspicuous than shorter ones. From the air, stands may have a different colour than the surrounding vegetation, especially where natural vegetation is not as lush as marijuana. Individual plants usually have a circular profile when viewed from above; this can be altered by bending or pruning the plant. Varieties which are naturally tall-growing may need to be cut several times during the season to keep them hidden.

Plants are sometimes cut back severely, to much as half their height when they get too tall, but this may damage the plant. A less drastic topping technique is to remove the opt foot of growth. Whenever new shoots get too tall they are clipped. But the plants should not be severely pruned late in the season when the growth rate has slowed (preflowering), because there will be fewer branches left on which buds can develop.

If you are trying to conceal plants behind a fence or wall, start bending or pruning the plants early, at about one month of age. By starting early and continuing to prune during the vegetative growth stage, you will train the plant to branch and fill up the area. If you wait until the plants are already tall, you may have to cut the plants back severely or clip shoots continuously.

Gardening Tips

Transplant Older Plants

A friend of ours was warned that his garden had been spotted by local authorities. Rather than cut down his four-month-old plants, he decided to transplant them. He dug the plants out, leaving a ball of soil about two feet square around the roots of each one. He wrapped each soil ball tightly in a plastic bag to transport it, and placed the plants in newly dug holes in a different spot. He kept the plants well-watered. After a few days, they recovered from transplant shock and started to grow once again. Transplanting large plants is not easy to do, but it could save a crop. The marijuana root system is not very extensive when the plants are in fertile soil with plenty of water; the tap root may only be six inches long on a ten-foot plant.

Wind Protection

Hemp Cannabis planted closely together has been used by farmers to form a windbreak to protect other crops. If you are growing in an especially windy area such as the Midwest, you may wish to plant a perimeter if tightly spaced Cannabis to protect your garden. Construct a rope and stick fence against the windbreak to hold the plants upright and prevent them from falling into the central garden. Simply keeping the plants clipped short is a simpler approach.

Inducing Flowering

Growers may wish to induce their plants to flower early, especially in the North, where the growing season is short. Plants in containers can be moved to a dark area for 12 hours of darkness or more per day. Black sheets of polyethylene film, dark plastic bags, and large appliance cartons can be used to provide periods of uninterrupted darkness. Use the dark treatment nightly until the plants are flowering (usually after one to two weeks of long-night treatments).

Winter and Spring Crops

In southern parts of the U.S., Hawaii and parts of California, you can grow more than one crop in a season. Greenhouses that stay above freezing can also be used for year-round growing. Plants started during the winter or early spring get naturally long nights and flower early, when they are relatively small, usually no more than four feet tall. Flowering can be postponed by breaking the long nights with short periods of light. This extends the vegetative growth period, yielding older, larger plants at flowering. Start breaking the night period with artificial light when the plant is about a month old. Continue the treatment until you want the plants to flowers. (See the discussion of photoperiod in section 3.)

Spring crops can be trimmed of buds when mature. The plant is left in the ground, and as the daylength increases, the plant will renew vegetative growth and flower once more in the fall. Plants can also be started in November or December indoors under lights and planted outdoors in February for harvest in April or May. The plants will grow faster under lights than they would outdoors under the weak winter sun. When they are placed outdoors, the long nights will induce flowering. By April the sunlight gets much stronger, perfect for flower development. Plants placed outdoors in February adjust easily to sunlight. Even so, they should be conditioned so that they do not suffer severe burn, as described in the Transplanting section in section 14.


Plants grown in areas where the weather is mild can survive winter when there are no heavy freezes. During the winter the plants will grow very slowly, but as soon as the weather warms, and the light gets more intense, the plants respond. This technique can also be used to obtain a second growth crop during Indian summers. The second growth is not as vigorous as the original, but is does increase the total harvest.

To prepare plants for rejuvenation, leave three or four pairs of lowers branches with leaves on the plant when you harvest. The leaves need not be large, but they must be green. Water and fertilise the plants. Within a few days the plants will show new growth.

The authors observed an outdoor container composed entirely of plants which survived a mild San Francisco Bay Area winter. These developed healthy second growth the following summer and flowered again in the fall. Some growers in Hawaii claim that their plants are three years old and that the plants have yielded as many as six crops of buds. Perennial marijuana plants also grow in Jamaica and Thailand.

Water Deprivation

Many cultivators begin to limit the amount of water their plants receive as soon as the flowers start to appear. Other growers give their plants as little water as possible after the middle of the plant's life. The plants are given small amounts of water only when they begin to wilt. (See section 9 on the reasons for stressing the plants.)

Under water stress many of the leaves may die and fall from the plant. Sometimes the plants appear "burned," and turn brown or gold. At harvest, water-stressed plants may only have buds left on them and these may have the colour, resin, and harshness typical of Colombian grass. These plants yield less grass at season's end. Not only are they smaller overall, but many of the leaves will have fallen away.

Water stress can be difficult to control in areas with heavy summer rain. Water-stressed plants often make up for their smaller size by a raped burst of growth after a heavy rain. One method of control is to cover the ground with plastic sheets when it rains so that most of the water runs off.

Tacks and Nails

Some growers hammer nails or tacks into the stems of plants several weeks before harvest. Many growers use long thick nails; others prefer to use several half-inch-long tacks. The nails are usually placed at the base of the stem. This is supposed to "increase potency." {Figure 72. Wilted plant. Unless watered it will die.}

Stem Splitting

This is a popular way to stress used by cultivators in the United States. The stem is split (not cut) at the base to from a space through the stem. Growers place a rock, small piece of wood, an old Cannabis stem, or piece of opium (in Africa) in the split. Sometimes the wound is bound with cloth or plastic. We don't recommend this procedure, and advise you to be careful not to kill the plants and ruin the harvest.


Outdoor growers are well-advised to plant several varieties of marijuana, because some varieties adapt to their new environment better than others. Also, each variety (and to small extent, each plant) has its own bouquet. By planting several varieties, cultivators assure themselves a varied selection of smoking material.

In areas with short growing seasons, many tropical varieties do not have a chance to flower. But immature material from these varieties may be more potent than mature flowers of a plant grown from seed of lower-quality grass. For instance, compare a flowering Mexican with a Colombian that doesn't. The Colombian may be better because the difference in varieties is so great. On the other hand, the Mexican may be better because it is flowering and has reached its full potential.


It is well-known that certain plants may be antagonistic to other species of plants, and that there are also beneficial relationships between species. Cannabis is known not to grow well among spinach 222. Although tomatoes and tobacco have been recommended as crops to avoid when growing marijuana, because of pests and diseases that these plants may harbor 67, marijuana grows very well in healthy tomato patches. Growers have also commented on how well marijuana grows when planted with corn, sugarcane, and beets.