Ask Ed

Ed Rosenthal is recognized worldwide as a leading authority on marijuana. In his 30-plus years as America’s “guru of ganja” he has written or edited more than a dozen books about marijuana cultivation and social policy that cumulatively have sold over one million. His first book, Marijuana Grower’s Guide, is the only title on marijuana cultivation to be reviewed by The New York Times Book Review. After almost two decades, his Ask Ed advice column continues to answer questions on all matters of marijuana from readers around the world.

STARTING A SIX PLANT MEDICAL GARDEN

I recently got my medical marijuana card and want to start a 6-plant garden. I have a flower area 140 cm x 110 cm x 170 cm tall, lit with a 400w HPS. Is that enough light?

Dan

Your garden has an area of about 1.5 square meters (M2). To grow high quality buds, plants require an adequate amount of light. Varieties differ in the intensity of the light they need to produce bountiful yields of high quality buds. Indica type plants require at least 500 watts per M2. Indica-Sativa hybrids need at least 575 watts. Sativa-Indica hybrids require about 650 watts per M2.

Use high-pressure sodium (HPS) lamps with reflectors that direct the light down to the plants. If your garden is filled with Indicas, use a minimum of 750 watts. Lamps of this wattage are not generally available. Instead, use two 400-watt lamps, or increase the yield by supplying more light. If they are available in your area, switch to a 1000-watt lamp.

For the Indica-Sativa hybrids about 900 watts of light are required. There are no 900-watt lamps so you could use either a 400 and 600-watt lamp or a 1000watt lamp if they are available.

The Sativa-Indica plant garden requires a minimum of 1050 watts. You could skimp a little by using 400 and 600-watt lamps together or a single 1000-watt lamp. The plants produce more with more light so you might consider two 600-watt lamps.

FOLIAR FEEDING

Is foliar feeding necessary?

Brinka

No. Plants can use their roots to deliver all the nutrients necessary for growth. However, they can absorb nutrients though their leaf stomata. These pore-like openings are used to exchange gasses such as oxygen and carbon dioxide and to regulate temperature and turgidity through transpiration and water absorption. If the water contains dissolved nutrients they are also absorbed.

There are several advantages to foliar feeding to supplement root feeding. First, the nutrients are used as much as 20 times more efficiently than when they are provided through the roots. They get directly to the plants. With root feeding only a small portion of the available nutrients are used.

Another advantage is that it gets to the plants much faster. This is especially helpful when there are indications of a nutrient deficiency.

Generally speaking you can dilute the nutrient solution to 25% and spray the leaves until they drip. Gardeners often spray the plants with compost tea, which provides available nutrients and also coats the leaves with beneficial micro-organisms that protect it from pathogens. If there is a dark period in the light regimen, spray in the early part of the lit period. Don’t spray more than once a week. Don’t spray after the first four weeks of flowering. You can use less fertilizer in the water/nutrient solution since the plants are getting some directly to the leaves.

Before trying this on your whole garden try it on a plant, or a part of a plant, first. Make sure to be a careful observer. If the plants are doing well continue, but if the plants react poorly to it, try another approach. One common problem is the water/nutrient solution is too concentrated. Try a more dilute solution.

LOW STRESS TRAINING

What is LST?

Buck

LST, short for low stress training, is a technique used to keep plants at a low height and to fill out the canopy. It can be used indoors or out. Auxin is a growth hormone produced by the growing tip that inhibits the growth of side branches. A common way of stopping its production is to cut off the top of the growing tip, Then the side branches, now uninhibited, grow in a rosette around the cut tip.

LST inhibits auxin production by bending the main branch, including the growing tip, so it is in a sideways position. As it continues to grow it is trained to continue horizontal growth. The side branches exhibit gravitropism; they orient themselves based on gravity. Since the stem is horizontal the branches start growing vertically. Each branch becomes a vertical stem. Keeping the main stem horizontal saves a lot of vertical space so it is convenient to use when it is at a premium. This is not its only advantage. It is an excellent way to grow large plants. Each of the side branches off the main stem becomes the equivalent of a vertical main stem. The single plant can spread out and become much larger than it would have if the main stem had been growing vertically.

There are many ways to keep the stem horizontal. Stakes, screens, and ties are often used. Indoors, the stem is often bent in a spiral within the container to conserve space within the canopy. However, in some circumstances it may be more convenient to keep the stem horizontal and straight. The advantage of that is that the new vertical stems line up in a straight row. Other advantages are that the plant does not grow as tall as it would have untrained, and does not have the stereotypical symmetrical canopy found in both top pruned and unpruned plants. Outdoors, to grow the largest plant possible, start it early, perhaps under lights indoors. Use supplemental lighting to prevent flowering. Set the light cycle so it breaks up the dark period for a few minutes several times each evening. Give the plant LST so it has a lot of vertical “stems”, each ready to produce side branches. Then let it grow out.

A similar technique is grow a plant in a container without pruning its top until it reaches a certain height, then turning it sideways so the main stem is horizontal. The container has to be modified so the roots can be watered from the new top and drained from the new bottom. The new side, which was the open top, must be sealed. The branches that were growing sideways will reorient themselves vertically and grow their own side branches.

The bottom branches have been removed to increase air circulation and decrease humidity. The lower portions were not receiving any light so they were not producing sugars and were costing the plant energy.

SEEDED BUD

I own a farm near Rome. I planted all my stash seeds so there are hundreds of plants of all sizes and styles growing on the property. I picked a few plants and found most of the buds were seeded. Some of the buds are ready, others still have unripe seeds. What should I do?

Fabrizio

Pick the buds as the seeds mature. Dry them. If the buds are all different and they can’t be identified by variety you may wish to process them in bulk. However if you can keep the plants or at least groups of plants separated, you will have varietals. Separate the seeds from the buds. This is done by getting the buds crispy dry and then rubbing them so the seeds fall out. Another method is to rub the buds against a mesh screen that is held tight using a frame. The holes are large enough for the vegetation to fall through, but not the seeds. Keep each group of seeds separate and mark them.

Marijuana produces THC to protect the buds from predators and disease. As the plant becomes more invested in reproduction it invests more energy into THC production so the ripening seed is most protected part of the plant. Marijuana from seeded bud has more trichomes on it when it’s growing than sinsemilla. You might notice that the seed cover, before it is disturbed, is covered with trichomes. It’s just that when you process it, many of the glands are lost. Other problems with seeded bud are that it produces much less usable material than sinsemilla and that it is often, although not always, contaminated with bits of broken or immature seed. If the now ground bud is seed bit free, it is suitable for smoking. If not, it should be processed into kief, water-hash or used for edibles.

LIGHTING A CLOSET

I have a 400-watt metal halide (MH) lamp lighting a closet that measures 80 x 160 cm. Is this enough light? Should I add another lamp during flowering?

Sergio R.

The 400-watt lamp provides enough light to grow the plants vegetatively. It will also produce nice buds in a garden filled with indica varieties. However, more light is required to flower indica-sativa and sativa-indica hybrids. This light might be supplied most easily using four 120 cm T-5 fluorescents placed on either side of the garden. They will produce the extra light that these varieties need to produce abundant tight, potent buds.

PREMATURE HARVEST

Can you harvest plants before the hairs change to colors from all white? Will you still get high from the buds?

Adam

The plants are weeks away from being ripe. There are some trichomes, the glands that contain THC on the flowers, but their caps are only partially filled with the THC resin and the terpenes, which supply marijuana its odor and personality. These flowers are immature and not ready to be picked. They have not reached their potential. They will be loose and will get you somewhat high but won’t provide you with the satisfying high you receive using fully mature bud. Would you eat a green peach?

TAKING CUTTINGS

I just got my license for medical use. We are allowed to have 12 plants in any stage of growth and 42 grams of dried medicine. I am thinking of starting 12 seedlings of two different varieties. I will be using feminized seeds so I will have 12 plants. I will select the best for cloning until I have 6 cuttings growing vegetatively until the next batch is ready.

When should I take the cuttings?

Santos

Take the cuttings just as the plants go into flowering. If you took a cutting from each of the 12 plants you would be double the limit. If you took 6 cuttings you would have to discard 6 of the plants that are growing. Neither is a wonderful prospect.

One idea is to set up two separate sections in your garden, the cloning/vegetative section and the flowering space. Start all 12 plants in the vegetative section. After a month place one of the plants in the flowering room. Then each week place an additional plant in the room. Approximately 8 weeks after placing the first plant in the flowering section you will be harvesting it. At the same time you would be taking your first cutting.

The problem is that to stay within the limits you would have to take the cutting before you know how good the plant is, and if you have an exceptional plant among the first eight, which went into the flowering room without having a cutting taken. Instead, after you harvest the plant use regeneration to bring it back into vegetative growth. This takes about three weeks. Meanwhile you have a chance to evaluate the bud and yield. If you like the plant, let it continue in regenerate, if not destroy it. Do this for each plant as it matures. Eventually you will eliminate all but the best plants.

The regenerated plants can be placed back into flowering once they have grown a bit. Most varieties grow extensive branching when they are regenerated. Prune off the smaller weaker ones so the plant puts its energy into growing the remaining ones larger. Once the plants regenerate, you can take clones from them to build up the numbers to replace plants that were eliminated. Once the population has stabilized, take a cutting for cloning from each plant as it goes into flowering.

If clones are available at dispensaries or patient self-help centers you may be able to purchase clones. This is a lot easier than maintaining your own clone center for several reasons. You don’t have to worry whether your clone has rooted, you are able to try preselected plants of varieties that you are interested in trying, and it speeds up your garden.

WATER STRATEGY FOR HYDRO UNIT

I have a 12 plant hydro garden using expanded clay pellets and a pump to trickle the nutrient solution. Do I need to let the nutrients trickle 24 hours a day?

Kanux

Yes. Trickle the water almost continuously. The roots metabolize and absorb water continuously since the plant continues life processes and growth both during the light and dark period. They absorb oxygen (O) from, and release carbon dioxide (CO2) into the water.

When water trickles over the pebbles they become covered in a thin film of water that has a high surface to volume ratio; a high proportion of the water has contact with air. The high surface/volume ratio facilitates the transfer of CO2 to the air and dissolving O2 from the air to the water. The large air spaces between the pebbles allow a lot of air movement so the roots always have access to O2. When water is pulsed so the stream ends and the water drains, a vacuum is created, which draws new air into the container. Then the stream begins again and creates a venturi effect, pulling air out, and of course, drawing new air in.

I had a system in which the pebbles received a stream of water from spaghetti tubing without drippers attached. The water was on for 5 minutes and then off for 1 minute. The containers were placed in a tray that that had a drain that was raised 5 cm, so they sat in a pool of water that was always moving and draining into the reservoir below. This served two purposes: It created a redundancy- if the pump should stop unexpectedly, there was enough water in the reservoir to keep the plants unstressed for at least a day. The other is that the roots grew out of the containers and slurped water directly from the reservoir.

The roots that grew into the water looked different than the roots in the clay pebbles. They were thicker and did not have the fuzzy root-hairs that grew from the roots in the container. They looked very healthy because they were growing in oxygenated nutrient-rich water. These roots spurred canopy growth.

SEEDS FROM HERMAPHRODITIC PLANTS

I had one plant in my garden that was a hermaphrodite. She mostly pollinated herself, although the buds on the other plants were very slightly seeded. Are seeds from hermaphroditic plants viable? Will the seeds from the hermaphrodite x female be hermaphrodites? Are any of the seeds worth starting?

Rogier

The seeds are viable. The seeds from the hermaphroditic plant are likely to be mostly hermaphroditic. They will yield lower quality, seeded buds. The seeds from the hermaphroditic x female crosses will result in some female and some hermaphroditic plants. It will be hard to differentiate the true females from the hermaphrodites until the plants start to flower. By that time you will have placed a lot of time and energy into growing those plants. Trying to “work” with hermaphroditic plants by removing flowers as they appear is usually a futile effort. It’s easier to start with regular seeds and sex them, feminized seeds or clones rather than seeds that produce plants that will be suspect during their entire flowering cycle. So, the seeds are not worth sowing.

Balconies and terraces can be used to flower plants. When used in conjunction with an indoor garden the size of the crop can increase dramatically. In mild and sub-tropical areas they can be used all year long. Long winter nights force the plants to flower as soon as they are placed outside.

REGENERATION

A friend of mine just recently gave me 4 plants that needed a home. They flowered them earlier than they wanted to (when they were about 25-40 cm tall) in an attempt to get some buds before they were kicked out of their house. I’ve set up a grow area for them and would like to know the best practices for reverting a plant back to vegetative growth. I’ve already got them under a 24-hour light cycle, but is there anything else I can do to help speed up the process and stress the plants as least as possible?

Jordan

To regenerate a plant, leave some vegetation and parts of buds on the plant when you are harvesting it and then place it back in vegetative under 20-24 hours of light daily and give them grow, rather than flowering formula fertilizer. Within a few weeks the plant will start growing vegetatively again. Once it has fully re-vegetated it can be re-flowered.

REMOVE FAN LEAVES

I recently read an article that recommended removing most of the fan leaves during the last half of flowering to enhance the size of the buds. It said that once flowering starts the large fan leaves have served their purpose. Is this true? Just about everyone else says don’t cut them.

DJ. Dickter

Everyone else is right. The leaves, which cost the plant energy and material to construct, are factories, which use light energy to convert CO2 and H2O (water) into sugar. The sugar is used as the core for building new tissue as well and for energy. When you snip leaves, you remove energy sources that are used to help the buds grow and for them to ripen.

The only time leaves should be removed from plants with developing buds is when the fan leaves shade the buds. Although the leaves provide energy it is more important for the buds to get direct light.

BUYING CLONES

A local dispensary has several varieties of clones for sale. Should I buy them or should I start my own? I want to harvest every couple of weeks. I go through about 30 grams a week.

Dan Too

You are better off buying clones. You have a legal plant limit in Colorado, so if you grow clones you are spending part of that limit on growing plants that are readily available. Buying rooted clones speeds up your process since it takes about three weeks to root clones, eliminates the time and worry involved in cloning and gives you the opportunity to try different varieties.

You should have two gardens. The first is to vegetate the clones you have purchased for one month. There will always be two plants in this space. Every two weeks a vegetating plant graduates to the flowering space. It will spend approximately 8 weeks in the space before it is mature. Varieties differ in flowering time so you may have to adjust the schedule a bit.

72 PLANTS

I live in Michigan, the 13th state to legalize medical marijuana. I am building a place for caregivers/patients to grow their medical marijuana legally. The maximum number of plants each patient can have is 12 and the max number of patients one caregiver can have is 6, including himself. My question to you is, how big should each grow room be with the maximum number of plants per caregiver being 72. How much power should each room have? Does each room need its own water source?

AJax Pr1me

You are allowed to grow a total of 72 plants but there is no limit as to how large a plant can be, so it would be in your interest to produce the largest plants possible. Let’s start from the trial plants, the ones that you will grow out from seeds or clones you have obtained. You will choose the initial varieties from these plants. Take clones from these plants that will also be grown out, then after evaluating the results select the ones you want to use. Grow out all the clones except for the plants you have selected as mothers, which are kept in vegetative.

Figure that your plants will be in vegetative cycle for about 10 weeks and then in flowering for about eight, a total of 18 weeks. All of the plants in vegetative can be kept in a single room. Keep the flowering plants in a separate room.

Dividing 72 by 18 results in 4, the number of plants that are to be started each week for the full regimen. Each week four large clones are cut from the selected plants to begin their 18-week journey. Once they have rooted they are placed in planting mix or large individual module hydroponic containers. They will remain in the vegetative room for a total of 10 weeks. During this time they will be given enough room and large enough rooting space to support a plant that will grow to a diameter of approximately one meter. The height is not as important as the width.

The plants will start out occupying a canopy space of 925 cm2, but by the time they leave the space they will be occupying about 8,400 cm2. So, you can figure that each plan uses an average of about 9325 cm2.

After about 10 weeks its time for the four plants to go into the flowering room, where they will spend the next 8 weeks or so under 12 hours of darkness and 12 hours of light. They will each occupy a space of about 1.5 m2. They are most conveniently lit using a single 1,000-watt lamp for each plant. If the largest lamp available is 600 watts use three lights over two plants.

These are going to be big plants, so the light should be kept high above them. There is a misconception that light energy dissipates with distance. The reality is that as the light beam spreads with distance its beam becomes less intense, but it delivers the same amount of energy. If the reflectors and their placement are designed to deliver the light to the plant canopy rather than disperse it to the walls or unoccupied space, the plants receive light from many directions, so less vegetation is in shadow. The other advantage of having the lights elevated from the plants is that there is less chance of foliage burn from heat and the plants get a more even light distribution. If the light were just a foot or two above the top of the plant the top canopy would receive far more light than the lower parts of the plant. When the light comes at a greater distance from different directions as a result of the wide beam from each lamp, the whole plant is more evenly illuminated.