Marijuana Horticulture Fundamentals is a comprehensive guide to cannabis growing and Cannabis Cloning, and we found it to be an excellent resource for new and experienced growers alike. Here is an excerpt from the chapter on cloning:
What is a Clone?
Cannabis Cloning creates an exact replica of the plant from which it was taken: same sex, growth pattern, and harvest timing. Literally dozens of successive generations can be obtained with no particular degeneration. Some growers take cuttings from mother plants, others from vegetating plants before they enter the flowering cycle.
Materials Called for in this Chapter
- One razorblade or very sharp pointed scissors
- One alcohol Bunsen burner
- Two 2-cup measuring cups
- One small bucket for carrying cuttings
- One mini-greenhouse dome and one propagation tray I Small potting containers / plastic drink cups with multiple holes in bottom for drainage
- Preferred medium (soil, rockwool)
- Fluorescent lights with cool white bulbs
- Rooting hormone (such as Wood’s Rooting Compound or Olivia’s Cannabis Cloning Gel) that contains butyric and acetic acid I Hand mister
- Clean, disinfected work area
Plants rooted from cuttings are the preferred method of propagation by many growers, particularly if they’ve experienced difficulties starting from seed, or if they want to be certain the offspring exhibit the identical traits of the donor plant. Cannabis Cloning is easy provided only a sharp, sterile razor blade or scissors are used to make the final cut on the stem. Cannabis Cloning solutions such as Wood’s Rooting Compound, a ready-to-use rooting compound (available from hydroponics supply stores), are used to minimize susceptibility to embolism (an air bubble inside the stem) and transplant shock; it also delivers hormones and nutrients to encourage rapid root growth.
Aside from viable cuttings, you will need propagation containers with an insert tray and a translucent domed top, as well as a sterile, inert medium to get started. There are many cannabis cloning machines and kits available on the market at your local hydroponics supply center. Fox Farms’ Light Warrior soil— mixed equally with a mix of one part Light Warrior, one part perlite, and one part vermiculite—is a good organic cannabis cloning medium. So are Grodan rockwool cannabis cloning slabs.
Cuttings require warmth, moisture, oxygen, and light. Inside the dome, try to maintain a humidity of 74–80% and a temperature of 75–80°F. To maintain the temperature, use a heated propagation mat placed underneath the tray that holds the medium. Root zone temperature should be slightly higher (say 3–5°F higher) than the ambient temperature inside the dome. These mats help monitor and maintain correct temperatures, usually about 15°F above room temperature. As such, the growth of root rot or “damping off ” disease is greatly inhibited.
Caution: to make sure your cuttings don’t get too hot, avoid placing cannabis cloning trays directly on top of heat mats. Elevate the tray two or three inches above the heat mat and monitor the temperature with a digital Hi / Lo thermometer.
Bear in mind that the heat mat will increase evaporation, so you must keep your growing medium moist. Not too moist, though: plastic covers and humidity domes can get too much heat and moisture, which can lead to fungal problems, such as pythium, so you should uncover them periodically, perhaps twice a day, or place a few small holes in the cover so that excess heat and moisture can escape. Once your cuttings form roots you can extend the period of time you keep the dome off of the plants, until ultimately the clones do not need to be covered at all, and are ready to be moved to the vegetative stage.
If you intend to transplant your clones outdoors, you must remember to acclimatize them in advance. As soon as the risk of frost diminishes, take your cuttings for a few hours at a time to an outdoor shady area protected from excessive wind, gradually increasing their exposure to the elements over a one or two week period.
Clone Considerations? Advantages?
Productivity; clones grow faster and accelerate the growth process more rapidly than plants started from seed; sex is usually pre-determined (female).
A batch of cuttings taken from the same plant will produce the same characteristics and yield uniform results.
Clones typically cost between $5 and $10 each, depending on the source, and going to purchase and constantly transport new clones is costly and potentially risky. At the same time, you can take dozens, even hundreds of clones from just a few vegetative plants by taking cuttings over and over again.
There are three general sources for clones. The first is an outside source, such as a friend or a legal Cannabis buyers’ club. The advantage of this is you save yourself time, space, and work. The disadvantage is the cost, unfamiliar genetics, and the possible introduction of pests and disease into the grow-room. Using outside sources also allows other people to know what you’re doing, which is never a wise move.
Keeping mother plants is another source. This enables you to perpetuate your genetics by taking cuttings from specific plants. In order to do this, keep a mother plant in a separate environment under an 18 on / 6 off light-cycle and never let it flower. Whether you’re just keeping one mother or ninety-nine, the same rules apply. You give it the same light as any plant in the vegetative stage. I’ve heard that some people retain the mother for years. Myself, I like to create new ones when they get too gangly—usually every six months or so. Mother plants allow you to self-perpetuate your plants and dictate your own schedule. They also afford you the knowledge that your clone source is disease and pest-free. On the downside, they eat up time, money, and space.
The third source for clones is to take them straight off your vegetating plants. This works only in systems where you have achieved a solid rotation, when you have just harvested your finished flowers and are about to move your vegetating plants into flowering. The trick is to wait two days after they have been placed under a 12 / 12 light-cycle; this purges them of starches that can inhibit root growth. Then take your cuttings from any or all of the lower branches, always leaving at least the top two for flowering. Once you’ve taken the cuttings, they can sit under fluorescents for up to thirty days before it’s time to transfer to your vegetating room. This completes the cycle and maximizes time and space.
Traditional Cutting Methods
Below are two traditional methods for taking cuttings. Both use artificial lighting, but you can choose to use a soil-perlite-vermiculite organic medium, a hydroponic substrate (such as rockwool or Hydroton Clay Pebbles), or one of many others.
Mother / Donor Plants
You should choose bushy plants with many small, 4–6-inch branches to take cuttings from. Cuttings root more easily when they come from a plant in its vegetative stage rather than in its flowering stage. For small gardens the best solution is to maintain mother plants. A mother plant is kept in the vegetative cycle all year by maintaining an 18 hours on / 6 hours off photoperiod. The goal is to keep the donor plant in vegetative growth and not allow it to flower or produce buds. Then you can cut off the branches whenever you want clones.
Gardex is a hydroponic substrate made up of a combination of mineral matter: vermiculite, perlite, and hydrophilic horticultural rockwool. Its water-retention capacity is 60% of its volume and the medium allows you to space out your watering intervals without fear of harming the plants. Gardex can be used for either automated watering systems or hand watering without fear of excess watering. Gardex is an excellent medium for rooting cuttings.
1. Maximum aeration of the root mass: 33% of the volume is made up of air I Higher water retention than soil?I Neutral pH (7)?I Accelerated growth and healthier foliage
2. Decreased watering frequency and easy rehumidification?I Consistent volume with no compaction?I Sterile because it is manufactured to contain no organic contaminants
Avoid Stagnant Water
Excessive water, especially stagnant water, increases the risk of rot, and the cutting will take longer to produce roots. Stagnant water is rapidly depleted of its oxygen by the plant and this prevents the growth of new root tissue.
Stake support the buds to prevent them from bending over and breaking stalks.
Cannabis Cloning On the other hand, aerated water promotes rapid root production and development.
Aeroponic Cannabis Cloning Machines
Cannabis Cloning machines (aeroponic propagation systems) such as the Rainforest by General Hydroponics, the EZ Clone, and the Clone Machine by American Agritech all work by directing a continuous spray of oxygen-rich mist onto the hydroponic substrate that holds the cuttings, which in turn encourages and promotes root growth. All of these propagation systems work very well and are available as both large and small models, producing just a small number of clones or as many as you need.
Rooting hormones are manufactured, synthetic hormones similar to those naturally present in plant tissue that induce root growth. Placing hormones on a freshly cut branch enables it to produce roots faster and with more vigor and health. You will save time and have higher success rates when using rooting hormones. Many forms of rooting hormones are available in liquid, powder, and gel forms. Powders are impractical: the powder must cover the cut stem in a thin layer, yet it clumps up and sometimes seals the stem, preventing it from taking up water and clogging its pores. Gels are more practical in that they adhere to the cutting and are easy to use; Olivia’s is a good gel brand. Wood’s Rooting Compound is also a good product. Liquid is ideal, however, because it penetrates the stem wall and can’t clump up or be wiped off as the cutting is placed in the media; here Vita Grow is a perfect option.
Types of Containers
Rockwool slabs are an excellent substrate and offer flexibility for the final method and system you decide to use. A rockwool slab, depending on the manufacturer, contains over 98 square 11/2 x 11/2-inch plugs; each square is its own grow cell that roots can develop in. The rockwool slabs can easily be cut in sections that fit your exact needs, but do not work with dry rockwool. Whole slabs fit perfectly into most propagation or mini greenhouse systems. Large plastic drink cups containing a media of equal parts of Fox Farm’s Light Warrior, vermiculite, and perlite also works well when only propagating small numbers of cuttings.
Water, pH, Nutrients
Use extremely low levels of nutrients in the rooting stage. Excessive salts found in fertilizers can block water absorption. General Hydroponics offer excellent pH-up and pH-down solutions; both are practical and work well, but use them sparingly and raise levels in small increments, thoroughly stirring the solution in between adding pH adjustment solutions. Do not use salt-based or synthetic pH-up or -down on organic soil or in organic nutrients. For organic pH preparation see the Water and Feeding chapter.
48 hours prior to taking the cuttings, you can prepare them on the donor plant for a higher rate of success. Choose the branches that will produce the best clones: nodes that are spaced every one or two inches; a succulent, green texture, not woody or hard. Lower branches are best for clones because they do not contain as much nitrogen and will root faster. All branches can root, some are just faster than others. On each prospective cutting, remove all of the lower leaves beginning at the lowest node, leaving only the top two to four youngest sets of leaves.
To cut off the lower leaves: hold the leaf and cut its petiole / stem with a razor blade, X-acto knife, or very sharp pointed scissors, one or two millimeters from the main stem. If you accidentally cut too close to the stem, it will cause unwanted damage. Using pointed scissors, cut off the tips of the two to four sets of remaining leaves to one half of their original size. This will stop the new clone from exerting too much energy on photosynthesis, respiration, or transpiration, and force it to produce roots.
Making these preparations 48 hours early enables the prospective clone to scab at places it has been cut and experience less stress when you take the cutting. Also, when using this method the risk of embolism is minimized to the final cut.
To remove a cutting, simply use a razor blade, X-acto knife, or very sharp scissors and cut the stem diagonally, three to four inches below the lowest leaf-free node. Immediately place the clone into a measuring cup filled with pH-adjusted, room temperature, pure, clean, filtered water. The stem next to the fresh cut will release its sap and an air bubble can form when it is exposed to the air for too long a period of time. This air exchange must be avoided or the stem will dampen off and suffer necrosis and the clone will rot and die.
Choose cultivars wisely. Just because it has the desired name, doesn’t mean it is a preferential copy of that cultivar.
Transporting Cuttings when Cannabis Cloning
Rooted clones may simply be placed in a container with a plastic bottom, or a bottom that won’t leak or absorb water from the media – not cardboard. Place a plastic catch tray in the container to help cuttings stay upright and keep them from sliding around or from being root damaged. Get the cuttings to their final destination as soon as possible. Do not leave them in a hot car or any such environment for extended periods of time. Unrooted cuttings can be transported by cutting them longer than you want them and then placing the fresh cut stem directly into pure water in either a small measuring cup or cutting tube (a test tube with a rubber seal on the opening that has a small hole which allows the cutting to slip in but not lose any water). Place the cutting upright in a sealable plastic bag, mist the inside of the bag, and seal it. This will prevent the cutting from drying out before it’s given its final cut and placed into its media. If possible, transport in cool, dark conditions.
As described in the Water and Feeding chapter’s Water Preparation section, the water you use for feeding your plants, especially when rooting fragile clones, should be filtered, decontaminated, temperature-adjusted and pH-adjusted, in order for it to be considered pure and safe for your cuttings and plants. References to ‘pure’ water in this text mean water that has been through this process.
There are many other methods of transporting clones and some will allow you to stall them for two or three days, yet as time goes by chances of success will diminish. I know of someone, for instance, who placed rooted clones into a videotape, sealed it in plastic and sent it wherever in the world he needed.
Cannabis Cloning Tips
Some growers make a few scrapes or superficial wounds on the base of the stem nodes’ bark when cannabis cloning. This will create a few sites where the hormonal activity is more concentrated. Basically, the plant will attempt to heal the damaged tissue and add cells that will ultimately aid in the generation of rapid root development. Never cut through the stem’s core; the goal is only to scrape through the stem’s outer bark (approximately 0.1 millimeters).
When inserting the cutting into the medium / container, avoid excess pressure and do not bend the cutting or force the stem into the medium. Cuttings are very delicate.
Most failures in cannabis cloning occur because of disease. Unsanitary environmental conditions are the foremost contributor to this problem. All areas used to handle, clean, and trim cuttings should be sanitized before you begin. If you plan on producing your own cuttings, start with plants from a reputable grower or seed bank. Mother or clone source rooms should be closely monitored to prevent disease and the introduction of insects. Wash your hands, and rotate and sanitize tools between taking cuttings from different plants. This will minimize disease and contamination.
Regular pest and disease monitoring of the clone source / mother plants will reduce potential problems in the propagation trays. It’s difficult to produce clones if mother plants are loaded with mildew or spider mites. Even clones from a reputable grower should be closely scrutinized! Be sure of the integrity of your source. You might be able to get a great deal on extra cuttings from another grower, but will you also be inheriting a disease or insect problem that will cost you more in the long run?
Always closely monitor the temperature and humidity of your environment.
The propagation environment should be managed to reduce fungal and bacterial disease. Sterile rooting media, benches, and tables eliminate a potential source of root-damaging diseases. Sanitize everything possible with a 10-to-1 water–bleach solution (or a 10-to-1 water-27% hydrogen peroxide solution) between crop cycles. Rinse everything afterwards. Bag and remove damaged and diseased plants and plant debris immediately. Inspect propagation trays each day. Continually removing infected, dying, and yellowing plant material reduces disease and dramatically reduces losses. Keep humidity levels at 74–80%. Irrigate and mist early in the day.
Stressed cuttings usually result from high light and low moisture levels. High light can be a problem during the early stages. Excessive light increases leaf temperatures, causing them to transpire and lose stored water. This contributes to cell collapse and dead tissue, making your clones easy targets for disease. Use cool white fluorescent lights, compact fluorescents, LEDs, or induction lights: they are more efficient, give off less heat than HIDs, and allow light and heat levels to be easily controlled by raising or lowering fixtures.
Getting Clones From Budded Plants
Minimizing moisture loss is the key to propagation. Once a cutting is harvested from a stock plant, the clock starts ticking. Keep cuttings misted and cool before you stick them in the growing medium, to reduce dehydration and increase rooting success rates. Cuttings should be stuck in the medium immediately following their removal from the mother plant. Delays add up to lost cuttings. It’s a good practice to apply a pure water mist once or twice a day for the first 24 hours. Cuttings should be placed in propagation trays with clear domed tops.
The Right Cuttings
Professional propagators go to great lengths to harvest the correct cuttings for cannabis cloning. Cuttings that are either too soft or too hard will present problems in the propagation trays. Also, cuttings that are too large will crowd neighboring cuttings, causing uneven rooting and promoting disease. Generally, soft cuttings taken from firm tissue will develop callus and roots quickly, and be relatively problem-free. Remember, the further from the growing tip the cutting is taken, the harder the tissue. This harder tissue roots slowly. Rooting hormones containing indolebutyric acid, Indole-3-butyric acid, or 1-Naphthalene acetic acid are a must for Cannabis Cloning; we use Wood’s Rooting Compound. Avoid dipping cuttings into a common container. This practice can spread disease from one clone to an entire group. To avoid spreading possible disease through an entire garden, it’s best to change your solution multiple times throughout the process when making many cuttings.
When cloning from mothers, take clones from wherever they’re available on the plant. It’s preferable to have at least two nodes above where you will be cutting. Your stage of growth and cultivar will ultimately dictate this, as an indica will have a shorter internodal length than a sativa. However, you want a cutting that is 4 to 6 inches long. Some people do a diagonal cut, some a cross cut; some use scissors, others a razor; it’s up to you. After cutting, there are those who scrape the side of the cutting to promote faster rooting. We trim the ends off all the leaflets and minimize all unneeded foliage. Your goal should be perfect uniformity in height. It’s best to take two or three times the number of cuttings you will need, so when the time comes, you will have a large stock to choose from and can select only the best specimens for your vegging system.
The correct medium can make or break your crop. We use Grodan rockwool slabs or Fox Farms’ Light Warrior soil with perlite / vermiculite amendments. Sterilized media are a must, and will help eliminate disease pathogens such as pythium. Media can sometimes dry out very quickly, causing root damage, so careful monitoring is required. The relationship of air and moisture separates a good medium from a bad one. A good medium is able to maintain a balance between the two variables. Too much aggregate can cause a medium to dry out too quickly and wilt cuttings. Too little aggregate creates soggy conditions that promote disease and fungal gnats.
Root-zone heating that maintains temperatures between 70–80°F is a good starting point. If your room does not already provide ideal temperatures, there are many thermostat-controlled heating mats available for purchase. Lower temperatures will slow plant metabolism and delay callus and root formation. A delay of even a few days can mean the difference between single-digit losses and catastrophe. Be aware that excessively high temperatures become a hindrance, too. Heat stress varies depending on the cultivar. Some tolerate temperatures well over 80°F, but most prefer high 70s and low 80s.
Rooting Hormones? Tips
I Wear rubber gloves to avoid contamination.?I Ventilate the room while working with it.?I Store the hormone in a dark, room temperature location.?I Avoid breathing it in or getting it in your eyes—wear goggles and a mask! I Clean spills with water. Remember to triple rinse.
Clones should be stuck 1 to 2 inches deep into the rooting medium (depending on your medium). Cuttings stuck too shallow are liable to be washed out of the medium or loosened to the point where rooting is delayed or inhibited. Cuttings stuck too deep may be in the part of the rooting medium cell that is constantly filled with water, depriving them of the air they need to callus. The base of cuttings stuck too deep will turn black and appear diseased. This means the tissue has died due to lack of oxygen. Once this happens, secondary infections can occur, killing the cuttings. Maintaining a proper sticking depth will produce uniform product.
Sticking cuttings at the correct density is an exact science. Crowded cuttings will stretch and be susceptible to botrytis. We use 11/2 x 11/2-inch rockwool cubes interconnected as a slab, and that dictates our spacing.
Fertilization and pH
We like to start our clones using 1/2 a teaspoon per gallon of both General Hydroponics Flora series fertilizers and 1/2 a teaspoon per gallon of liquid vitamin B1. Adjusted to a pH of 6.2, we use this mix to flush the medium. We only use the B1 on the first flushing / feeding, and then switch to the fertilizer alone. We water the medium every three days, but your environment will ultimately determine your schedule. With the first callus, cuttings begin to take up moisture from the medium.
The Rooting Process—Toning
Rooting cuttings is a multistage process. Stage 1 is where the cutting develops callus. Callus is basically where the fresh cut seals itself like a scab. This keeps it from losing moisture, enabling it to encapsulate and retain the moisture it already has. During stage 2, the first root initially develops. Stage 3 is when the shoot and root tissues develop. Stage 4 is for toning the cuttings prior to transplant. This step is often overlooked. This process should begin at least one week before planting and consists of increasing light levels and exposure to vegetative growth conditions. Clones that have been properly toned will respond to the environment shift that occurs in the finished containers with little or no wilting and subsequent leaf damage.
Cannabis Cloning is a simple method to determine the sex of plants. Take cuttings as described, except place the fluorescent lights on a 12 on / 12 off flowering light cycle. Cuttings will show signs of being male or female in approximately 14 days. This is the proper method of sexing plants. Inducing the whole plant to flower instead of a clone causes stress, plus you will have wasted two weeks of vegetative growth, unless you plan to flower at that time. Taking a clone and sexing it makes much more sense when cannabis cloning.
Signs of visible roots produce a gratifying sense of satisfaction. After about seven days for faster cultivars and up to 14 for slower cultivars, the cuttings will develop roots. Allow the roots to develop and grow for approximately five to 10 more days until they are ready to re-pot or be installed in a hydroponic system.
We hope you enjoyed this chapter on Cannabis Cloning.