Marijuana Grower's Handbook

by Ed Rosenthal

  These plants were tied to a horizontal pole to keep them from growing taller.

  SUNLEAF (FANLEAF) REMOVAL FOR LIGHT

  Contrary to myth, most sun or fan leaves should not be removed from the plant during the vegetative stage. These leaves are costly for the plant to produce, and they are sugar factories that turn light into chemical energy. These sugars are used to power metabolism and are also used for tissue building by combining them with N and P to make amino acids and proteins. When a leaf is removed, the plant loses a source of energy, and its rate of growth slows. Gardeners who routinely remove the fan leaves from their plants outdoors slow growth and lower yields.

  If you don’t believe this, try an experiment. Use a plant that has two sun leaves opposite each other with a small branch growing from either side. Remove one of the leaves and see which side branch develops faster.

  Left to right: 1. A one-bud plant tied to a stake for support. 2. With two buds each stake holds one bud firmly in place. 3. With three buds the stakes hold the buds upright and spaced from each other. 4. Four- bud trims work really well for plants in containers with a diameter of 10-12” inches (25-30 cm).

  Sometimes a few fan leaves block light from a large section of a plant. These leaves can be removed if, on the whole, the plant receives better distribution of light.

  Similarly, leaves that are constantly in shadow such as leaves below the canopy indoors are not contributing to plant growth, so they should be removed. Similar to “lollipop” pruning, this eliminates the risk of infection, improves air circulation, lowers humidity, and reduces the demand for nutrients.

  Leaves that are directly blocking light from getting to buds or the cola should also be removed. This becomes more apparent as the buds grow and become more prominent. However, leaves near the buds but not blocking light should be left in place.

  This plant has only a single bud, which allows it to spend less energy developing its infrastructure and more energy developing its flowers. With only a single bud the plant doesn’t spend much time developing infrastructure.

  Remove yellow leaves, as well as any infected or infested material.

  SINGLE-BUD PLANTS

  Plants can be put into the flowering cycle when they are only a foot or two (30-60 cm) tall, before they have developed branches. They grow into plants with only one bud. The main stem becomes swollen with flowers, but there is little to no branching. These plants are useful for compact gardens because they require only between one quarter to one square foot (7-30 sq cm) of floor space.

  BENDING AND CRIMPING

  Bending should proceed carefully, to avoid breaking the stem or branches. The plant will repair damaged stems if there is some snapping or pinching, so long as the stem is not severed or split. Young branches that are still green are more flexible than older ones that are woody and have turned tan or brown, which cannot be bent much before they snap.

  One method of bending the branch is called crimping. The goal of this technique is to stress the branch by twisting top stems so the plant will reinforce the damaged area. The plant repairs the damage quickly. The stem remains bent and the repaired area is stronger than it was before it was treated.

  To crimp a stem or branch, use one hand to hold the stem in place. With the other hand, gently twist the stem back and forth by rolling it between your thumb and forefinger until you feel tissue crunching or snapping. On larger branches, an audible break indicates that the twisting has damaged the stem. Smaller branches can be pinched rather than twisted.

  Large rings hold each plant firmly in its own space.

  TOMATO RINGS

  Plants can be “opened up” to allow more light to lower branches in the interior. This usually entails positioning branches so they don’t shade the interior or so that they get more light themselves. String, rope, cloth, gardener’s tape, twist-ties, stakes, and braces are all useful for bending branches to your will. Also, plants can be controlled by keeping all branches inside the cone. This way they are kept within a designated canopy area.

  Tomato trellises (the metal cones) can be used to open up the plants when they are still young. The branches all get more light from the opening and respond by growing bigger buds. Position branches around the outside of the cone, and tie them to it using twist-ties or plastic gardening tape. Indoors, these conical trellises can be used to contain unruly plants. A canopy of sativas and other large plants can be confined so they don’t infringe on their neighbors using the four or five foot (1.2-1.5 m) cones.

  This ring was placed in the ground inverted. The branches were tied up outside it to open them up to light.

  You can also train your plants using a trellising technique commonly used by grape growers. Stretch ropes at one foot (30 cm) spacing between posts. Tie the plant branches to the ropes. Stretch each branch horizontally so the plant has virtually no depth.

  Alternatively, use chicken wire attached to a frame as a trellis. As the plants grow, use twist-ties, gardener’s tape, or soft string or cloth to attach them to the wire.

  INVERTED TOPS, SUPERCROPPING, BENDING

  Removing the top bud stops growth-inhibiting auxin production so the lower branches begin to grow. A way to achieve this result without the loss of the top bud is to bend the top bud down. When it is positioned at a height below the side buds, it stops producing auxin. The side branches are no longer inhibited, so they start growing. At this point the main bud can be released and it will start to grow again. This results in more very large buds.

  Metal framing around the outside of the plant gives it support and keeps the branches within its perimeter. The wooden frame on top opened the branches so more sunlight could reach the interior.

  Framed netting is used to support the buds. The netting is put in place before the plants reach their ultimate height. As the buds get larger, they are supported so they don’t fall over.

  Stakes were placed around the plant. Then rope was strung around the posts to keep the plant within their perimeter.

  Supercropping is a similar technique of training top branches to grow horizontally so that the primary bud is exposed to more light. With more areas exposed, the bud grows larger than normal. This technique can also be used when one bud is growing taller than the rest of the canopy. Position the branch by bending, tying down or gently snapping it.

  There are several ways to tie the top bud. The top of the stem near the growing tip is composed of flexible soft green tissue, so it can be gently bent down or sideways. To secure the stem and branches, use soft string or cloth, gardener’s tape, twist-ties or stakes. Keep any knots loose to minimize damage. The branch may have to be supported by splinting with a skewer or bamboo suppport.

  When the top branch is bent so that it is positioned lower than some of the side branches, the side shoots grow as if the top branch was cut. After the side branches have started growing, you can release the top branch so it can grow upward again. Branches produce more growth than they would with the top branch dominating. The plant with a group of branches produces more bud weight than top dominant plants.

  FLOWERING

  Photo: Rachael Szmajda

  Marijuana is a short-day plant. As the days get shorter, marijuana determines when to flower based on the number of hours it receives of uninterrupted darkness. It measures the length of the dark period using the hormone phytochrome, which has two states. The hormone’s inactive state, Pfr, occurs when it absorbs red spectrum of light at 666 nanometers. It also has a slight sensitivity to blue light. The hormone changes to its active form, Pr, over a period of two hours when the plant is in darkness. When the Pr flowering hormone levels remain high for a critical period of time over several days, the plant changes from vegetative growth and initiates flowering.

  The number hours of darkness plants need to initiate flowering differs by variety. Sativas require a longer period of darkness than indicas because they developed near the equator, where the length of daylight is much more consistent than at northern la
titudes, where indicas developed. Some sativas continue to grow vegetatively with 10 or 11 hours of darkness, which usually cues most plants to flower.

  Many sativas initiate flowering only when the dark cycle increases to 12 hours or more, which occurs September 22 in the Northern Hemisphere.

  By contrast, most indicas flower with 8 to 11 hours of uninterrupted darkness (13 to 15 hours of light). In southern tiers of Europe and the U.S., a few indica varieties flower as early as June 22, the shortest night of the year. For this reason, outdoor gardeners in these regions should consider sativa-indica hybrids and sativas. In the central and northern tiers, indica and indica-sativa hybrids usually start flowering in August and are ready to harvest in September through mid-October.

  Some sativas and sativa hybrids require a longer dark period at the end of flowering to fully ripen their buds. Outdoors, this happens in due course as the nights lengthen in the fall. Indoors, change the lighting regime to 14 hours of darkness/10 hours of light to promote ripening. This is especially helpful in finishing low latitude varieties that don’t reach maturity in their native lands, where there is no winter, until the middle of the short-day season.

  INDOOR FLOWERING

  Flowering time of female marijuana plants is regulated by the length of the uninterrupted dark period, so gardens under lights can be forced to flower at any time with the flick of a timer switch.

  Look a few nodes down from the plant top. A small flower sometimes grows presaging the plant’s sex, allowing the gardener to identify its sex.

  To determine when to flower the plants, look down at the canopy. When two-thirds of the floor space is hidden by plant canopy, it is time to start the flowering process. The remaining space will fill in during the flowering stage. You may need to consider not only the breadth of the plants but also their height. If the garden has height limitations, the plants should be forced to flower before they get too tall.

  Sativas grow the most after forcing—typically an additional two to three feet (60-90 cm). Sativa-indica hybrids increase in height by one to two feet (30-60 cm), indica-sativa hybrids one to one and a half feet (30-45 cm), and indicas grow up to one foot (30 cm).

  To force flowering, lights must be turned on and off with consistent regularity, and the darkness must be uninterrupted. For that reason, it is essential to use a timer to regulate the lights. Set the timer so the lights stay on for 12 hours and then remain off for 12. Within a week, you will notice a change in growth. The plants are responding to the new light regime and are beginning to flower.

  You do not need to taper the light change. Reduced light from 18 hours daily (or continuous) down to a flowering cycle of 12 hours of light and 12 hours of uninterrupted darkness with no intermediate steps. The change in the light regimen does not shock the plants.

  SINSEMILLA & SEXING

  Marijuana users prize seedless female flowers, known as sinsemilla because they produce far more useable buds than seeded buds; nothing is wasted on seed production. Sinsemilla is also more attractive and far more convenient to use. Marijuana seeds have an obnoxious oily odor when they burn, so they need to be removed before smoking. Sinsemilla buds are seedless, so there are none to remove.

  In order for female flowers to ripen without seeds, they must remain unpollinated (unfertilized). Because cannabis is dioecious, male and female flowers appear on separate plants and must be kept seperate. If you are growing from unfeminized seeds, roughly half of what you germinate will be male and must be removed from the space as soon as they can be identified. This culling should be done early in the male plants’ development, before any large flower clusters appear. Even a single open flower can release enough pollen to fertilize dozens of neighboring female buds.

  Marijuana can be sexed early. There are two basic methods:

  1.Identifying early, premature flowers

  2.Forcing plants to flower by altering the light regimen

  There are several ways to use the forcing method, each with pros and cons.

  Visual identification of the plant gender is easiest, since it requires no intervention. Sometimes, while a plant is growing vegetatively, a single, small flower appears at the space where the leaf joins the stem (node) two to four pairs of leaves from the top. The sex of the plant is the same as that flower. This method is also the easiest to get wrong, since identifying the tiny, premature flowers can be challenging, and not all plants produce them. Use a magnifying glass or photographer’s loupe to get a clearer image.

  Dusk and dawn differ from sunrise and sunset. They occur preceding and proceeding dawn and dusk, respectively. They represent the time the light gets to Earth before sunrise and after sunset.

  Forcing plants to flower is a more certain method. Since flowering is regulated by the number of hours of uninterrupted darkness plants receive each day, it’s easy to manipulate them to reveal their sex. Establishing a long-night regimen for a week forces them to indicate. Then remove the males from the garden, (or separate them if you are to breed) and returned the garden to the vegetative growth cycle by changing the light regimen back to the long day/short night.

  A good alternative is to take a cutting from each plant and force it to flower. Carefully tag each cutting to identify which plant it came from. Set the clones in a grow medium and provide a light regimen of 16 hours darkness/8 hours of light. Within a few days, the clones will indicate. Since each clone has the same sex as its parent, you have identified the parent’s sex without taking it out of the vegetative stage and disrupting growth.

  You can keep the female clones under the flowering regimen to get a tiny taste of the parent’s future buds. This also allows you the opportunity to eliminate weak plants. Be careful to label cuttings and plants so you can match them up accurately once they’ve been sexed.

  BLUE LIGHT

  Blue light is another option for sexing. As mentioned earlier in this chapter, marijuana flowering is very sensitive to red light of specific spectrums. Any interruption of the dark period with light that contains the red, 660 nm spectrum returns the flowering hormone Pr back to its inactive state, Pfr. This prevents flowering.

  Blue light at 400-450 nm also has an inhibitory effect on flowering, but its effect is weaker than red light. Plants grow some flowers when blue light is kept on during the dark period; however, they continue to grow vegetatively as well. If you use blue LED or fluorescent lights to provide the plants with nothing but pure blue light, they will get enough stimulation to produce some flowers for sexual identification but not go into full flowering mode.

  PHYTOCHROME RESPONSE

  Phytochrome response chart shows phytochrome Pr-Pfr sensitivity across the light spectrum.

  This is a good sexing technique to use anytime, but especially when a large number of plants are involved. No cuttings need be taken and matched to their mothers, so there is no chance of a mix-up or dead, non-indicative clones. As soon as a plant produces male flowers, eliminate it from the space. Once all the plants indicate, replace the blue light with a full-spectrum light period to keep the plants growing vegetatively.

  Plants use blue light to regulate flowering as well as for photosynthesis. Blue light is not as efficient a source of energy for photosynthesis as red light indoors because blue light has a higher energy value than red light and it requires more energy to produce than red light. However, the plant obtains the same amount of energy from both of them. When blue light is turned on during the dark period, plants photosynthesize, but the growth from the blue light is not significant. The stems grow a little more stocky.

  Flowering is a localized response by the plant. When one part of a plant is placed in a flower-inducing dark period, but the rest of the plant is not, only the part under the reduced-light regimen flowers. This is also a viable technique for sexing plants.

  The effect of blue light on flowering is more important to us. See the Phytochrome Response chart, which shows phytochrome Pr-Pfr sensitivity across the light spectrum. The red-far-red portion sho
ws high activity. The blue spectrum shows just a little bump. This indicates a slight activity. The result is sporadic flowering on all the plants.

  You can create a pure blue light with LEDs and blue CFLs. Use about 200 watts of mixed blue light per 1,000 watts of regular light. I have done only initial experimentation with this so test this in a limited way first.

  ABSORPTION SPECTRA OF PHYTOCHROME

  Plants exposed to pure blue light peaking at 400 nm with effects at 400-450 nm during the dark period produce a few flowers but continue growing vegetatively. In this way blue light is used to force plants to indicate sex without interfering too much with vegetative growth.

  THE FLOWERS

  Identifying the sex of marijuana flowers is easy once you know their characteristics. Male flower buds look like balls dangling from thin stems, with a curved protrusion at the bulb’s end that comes to a blunt point. As the male flower ripens, the head’s position moves from hanging down to upright. The petals that formed the bulb open, revealing five simple petals that range in color from cream to yellow. Each has a stamen in the middle that releases pollen to a breeze or wind.