Marijuana can be reproduced (propagated) sexually or asexually. Seeds are the product of sexual propagation; clones or cuttings are the result of asexual or vegetative propagation. In its simplest form, taking a cutting or clone is cutting a growing branch tip and rooting it.
Making clones is the same as taking cuttings and is still the most efficient and productive means of cannabis propagation. (Technically, cloning is taking one cell of a plant and promoting its growth into a plant.)
Once the sex of a plant is known and it is a female at least two months old, you are ready to practice the simple, yet incredibly productive art and science of cloning. If the climate is poor, the plant will develop poorly and be stunted. If the grow room is well maintained with a perfect climate, strong healthy plants will be harvested.
Cloning reduces the time it takes for a crop to mature. Productive growers have two rooms, a vegetative/cloning room, about a quarter the size of a second room used for flowering. Smaller vegetative plants take up less space than older flowering plants. For example, a 250 or 400-watt metal halide could easily illuminate vegetative plants and clones that would fill a flowering room lit by three, 600-watt HP sodiums. Fluorescent lamps are more economical and work well to root clones if the halide is turned off.
Combine 8-week flowering/harvest cycles with continuous cloning to form a never-ending perpetual harvest. Another scenario is to take one clone every two days and harvest one plant every other day. Every time a plant is harvested, a rooted clone is moved from the vegetative room into the flowering room to take its place. This regimen gives a grower 60 flowering clones that are on a 90-day schedule. It takes 90 days from the time a clone is cut from the mother plant until the day it is harvested. Using this schedule, a grower would have 45 clones and 30 flowering plants growing at all times.
Clones are induced to flower when small, 4-12 inches tall. Short plants make most efficient use of HID light. Artificial light diminishes to the square of the distance, which means that foliage 4 feet away from the bulb receives 1/14th, that’s right one fourteenth, as much light as if it were one foot away. Foliage that is shaded or receives less light grows slowly and spindly.
Well-illuminated, strong clones grow fast and have less chance of being affected by pests and diseases. In fact, fast growing clones develop faster than spider mites can reproduce. By the time a spider mite infestation has taken hold, the plants are harvested.
Clones are also easy to submerge completely in a miticide when small. Submerging clones in a miticide before moving them into the flowering room greatly diminishes mite populations.
Short crops of clones in small containers are much easier than big plants in big containers to move in and out of a grow room for cleaning and sterilization. Rooms that are regularly disinfected have fewer problems with pests and diseases.
Experiments with clones are more consistent and easier to control. Genetically identical clones respond the same to different stimuli, such as fertilizer, light, bending, etc.
Hormone Signals and Cuttings
Cuttings respond to signals initiated by d hormones, temperature and light. Plants use these signals to interpret their environment and react to it. Growers control plant responses with synthetic hormones or influencing natural hormones.
Here are the five most common hormones that affect cannabis growth.
- Auxins control whether plants grow leaves upward toward light or downward toward the center of the earth. Auxins are growth signals created in a plant with the main concentrations found in the growing tips. Concentrations of auxins make plant parts do specific things, like grow toward light or grow downward. Auxins in growing tips and buds are redirected during the course of a week to the wound when a clone is taken. Once the auxin concentration is adequate it sends a signal to root primordial to grow.
- Cytokinins stimulate cell division. They send signals from roots as to what to expect.
- Gibberillins signal more than 90 events including cell elongation and new cell growth in seeds.
- Abscissic acid (ABA) hormone, unless modified by other signals, is the general “stop” signal for plant growth.
- Ethylene signals fruit to ripen and season end.
Stress disrupts hormones and slows rapid growth.
Internodes Stretch Because:
- Giberillin concentration is improper
- Day/night temperatures have disparity of more than 3-5 degrees C.
- Low light concentrations
- Plants receive too much light
- Plants can stretch at internodes to become the same height as surrounding plants.
Plant Age and Young Growth
Hormone content dictates a clones rooting ability. A mother plant has three distinct hormonal “age” zones. The top of the plant and the tips of the branches are hormonally the oldest part of the plant. The base and the lower stems are the oldest regarding hormones. The best place to take cuttings is in this zone, where hormonal concentrations are the best for rooting.
Hormone content is different in different parts of a plant. Root growth hormones are concentrated near the base of the plant near the main stem. This is the oldest portion of the plant, but where the most root hormones are located. The top of the plant contains older hormones and cuttings taken from this part root slowly. The middle of the plant supports moderate levels of hormones.
To Maintain Integrity in Clone Stock:
- Maintain 18-hour photoperiod
- Keep plants healthy
- Grow mothers 6 months or less
- Grow hydroponically
Any female can become cloning stock, no matter how old. She can be grown from a seed or clone. The important thing to remember when taking clones from a mother is to never let the mother bloom and then revert back to vegetative growth.
Keep several mothers in the vegetative stage for cloning stock. Strong mothers produce strong healthy clones. Start new mothers from seed every year. Clones have a better chance of being strong and healthy when mothers are not stressed. Mother plants must have at least 18-hour days to retain a strong of genetic characteristics.
A clone is an exact genetic replica of the mother plant. Each mother’s cell caries a DNA blueprint of itself. Radiation, chemicals and poor cultural practices can damage this DNA. Unless damaged the DNA remains intact. Clones that grow poorly are generally the result of unsanitary and poor cloning practices.
A female plant will reproduce 100 percent females all exactly like the mother. When grown in the exact same environment, clones from the same mother look alike. But the same clones subjected to distinct environments in different grow rooms often look differently. For example, a broad-leafed indica clone that is under-fertilized and grown in a low-humidity environment will look different than a perfectly fertilized sister clone grown in a humid environment. However, mutations can occur and environmental stress can cause an occasional male flower on a female plant.
A month-old clone from a six-month old mother is not really one month old; it is six months old, just like her mother. This phenomenon is not totally understood, but valid. A six-month old plant produces more cannabinoids than a one-month old plant. By cloning this THC-potent plant that will continue to grow in potency at a very rapid rate.
Always start with the best cloning stock you can find. Mother plants yield clones in her image. If the mother plant lacks potency, harvest weight or is not pest and disease resistant, the clone shares her weakness. This weakness is compounded when growing only one variety. An unchecked pest or disease infestation could wipe out the entire crop. Keep mothers healthy. Many growers do a preventative spray weekly.
Each time a mass cloning is made, new growing shoots are initiated. This new growth develops healthier roots faster that grow quickly. Mothers must be constantly pumped-up to continue to produce new growth. Give mothers about 10 percent less nitrogen because less nitrogen promotes rooting in clones.
Weekly spraying keeps mothers from risk of disease and pest attack. Never take clones from sick or diseased mothers. They will grow poorly and yield low.
For best results take clones from mother plants at least two months old. Plants cloned earlier may develop unevenly and grow slowly. Clones taken from flowering plants root quickly but require a month or longer to revert back to vegetative growth. Such rejuvenated clones occasionally flower prematurely and buds are more prone to fungal attacks.
Clones suffer stress and go through an incredible transformation when they change from a severed growing tip to a rooted plant, their entire chemistry changes. The stem that once grew leaves must now grow roots in order to survive.
While rooting, clones require a minimum of nitrogen and increased levels of phosphorus to promote root growth. Sprays should be avoided during rooting as they compound cloning stress.
Root inducing hormones speed plant processes. When the stem of a cutting develops roots, it must transform from producing green stem cells to manufacturing undifferentiated cells and finally fabricate root cells. Rooting hormones hasten growth of undifferentiated cells. Once undifferentiated, cells quickly transform into root cells. Three substances that stimulate undifferentiated growth include napthalenaecetic acid (NAA), indolebutyric acid (IBA) and 2,4-dichlorophenoxyacetic acid (2,3 DPA). Commercial rooting hormones contain one, two or all of the above synthetic ingredients and often include a fungicide to help prevent damping-off.
Rooting hormones are available in different concentrations. Always use the weakest concentration for softwood cuttings. Use only one application of a rooting hormone containing IBA. Any IBA application that is overdone or lasts too long will inhibit rooting. Clones direct their own auxins to the wound made when the cutting was taken. If the artificial rooting hormone has not dissipated concentrations would be too high.
They are available in a liquid, gel or powder form. Liquid and gel types are the most versatile, penetrate stems evenly and are consistent. Powdered rooting hormones adhere inconsistently to stems, penetrate poorly, spur uneven root growth and yield a lower survival rate.
Split the stem of clones to expose more of the cambium layer, the only place that generates new roots.
Before you make clones
Small clones with few leaves root faster than big cuttings with many leaves. At first leaves contain moisture, but after a few days, the stem is no longer able to supply enough moisture and the clone suffers stress. A small amount of leaf space is all that is necessary for photosynthesis to supply enough energy for root growth.
Large cuttings with much stored starch root slower than small clones with small stems. The excess starch in a moist soil environment also attracts problems from pathogens.
Although thin-stemmed clones have fewer reserves (starch) they only need enough reserve energy to initiate root growth.
Do not use fertilizer. Do not kill clones with kindness by giving them nutrients. It will delay rooting. Ammonium nitrate, a very common fertilizer, will stop root hairs from growing. Seaweed: Nutrient extracts including seaweed and algae contain hormones (cytokinins) that promote green growth and delay root growth.
Do not add more rooting hormones. Rooting hormone concentrations within clones are critical. Clones also generate (rooting) hormones. Adding more hormones (IBA, auxins and cytokinins) will disrupt the natural balance and delay rooting.
Use anti-desiccant sprays sparingly and only if a is impossible to set up a humidity tent. The semi-permiable synthetic anti-desiccant spray coats leaves and allows gasses to escape but not water vapor. Make sure to cover foliage evenly when applying. Even with a coating of anti-desiccant wax, clones may suffer moisture stress. Make sure to keep the root zone moist. Inadequate moisture causes root development to stop.
Always keep the cutting area clean. Stay away of areas that could harbor fungus spores. Pythium is the worst! Pythium flourishes in high temperatures and excessive moisture. Temperatures from 65-78 degrees F. (18-25 degrees C.) impair germination of most spores.
Mites, whiteflies, thrips, etc. love weak tender clones. Infested clones should be separated and removed from the room to avoid spreading. Cooler conditions slow mite reproduction and allow you to avert an infestation.
If an infestation does occur, apply aerosol pyrethrum. Remember all pesticides, natural or not, are phytotoxoc. Spraying cuttings is a bad idea in general. If you must use sprays, use them when it is cool and only natural organic sprays and keep them to a minimum.
The last thing to remember is to grow more clones!