Many marijuana horticulturists operate a perpetual garden. This means as soon as one crop is harvested, there is another crop to take its place and the grow cycle continues uninterrupted. In order to have a perpetual garden without any glitches, a grower must master the art of cloning his or her marijuana plants. Cloning is the preferred method of propagation for most marijuana growers because it ensures a genetic duplicate of the plant from which the cutting or clone was taken.
Cloning also allows a grower to continuously propagate female plants and seedless female flowers are what most marijuana horticulturists are trying to grow. It also allows a marijuana grower to continuously grow the best strains for their particular environment. In other words, when a grower finds a plant that has the desired attributes (high quality, high yielding, etc.), he or she can clone that plant and create an entire garden of that strain. There are a variety of cloning techniques that can be used, but all share the same goal: to create healthy young plants with established root systems that can be put into the vegetative stage of growth.
The first step a cannabis grower must take in the cloning process is selecting a mother plant. Aside from having the desirable qualities that make the grower want to clone it, the mother plant should be healthy and free of stresses, diseases, pests and pathogens. This is because when you clone a plant, the resulting clones can retain any problems that were affecting the mother plant at the time of cloning. Put another way, if the grower takes a clone from an unhealthy mother plant, chances are good that the clone will also be unhealthy. A good rule of thumb is to closely examine a mother plant a few days prior to cloning. Be sure to look closely for insect damage, molds or fungi and check the overall health of the leaves. Most cannabis growers like to take clones from a mother plant while it is in its vegetative stage of growth. Clones taken from a mother plant in the later stages of fruiting or flowering will usually result in lower success rates.
The process of cloning marijuana plants by taking cuttings is fairly straight forward. Cloning by taking cuttings is exactly what it sounds like: a cutting or a section is taken from the mother plant and that section is turned into a new, individual plant. For most plant varieties, this entails cutting a small section off one of the branches (usually 2-6 inches in length) and placing the cut end into a clone medium. Unlike other areas of the marijuana garden, cloning doesn’t require a lot of equipment. In fact, many cannabis growers claim a very basic clone set up is the most effective. A basic clone set up may include no more than a propagation tray, humidity dome, seedling heat mat and a medium conducive to rooting.
When taking cuttings, it is best to make a 45 degree angle cut just above a node site (the place where a leaf or branch attaches to the main stem). After making the cut, the cutting should immediately be dipped in cloning solution or gel and placed into the clone medium.
Although some can be cloned in straight water, many marijuana varieties develop roots faster when placed in some sort of inert grow medium designed for root development. Stonewool, coco fiber, peat moss, perlite and clay pebbles are examples of inert media that cannabis growers can use to root clones. There are even some specific clone media products on the market. Some cannabis gardeners choose to place the freshly cut clones into a light soil mix for rooting. In many ways the medium chosen is personal preference. As long as the medium has the ability to hold some moisture and provide oxygen to the developing roots, it should work just fine.
Unstable atmospheric conditions may be the biggest cause of cloning failure by novice growers. A temperature range of 72-80 degrees F for marijuana clones is usually optimal. If obtaining these conditions in the greenhouse or indoor garden is not possible, it may be necessary to create a specific cloning area elsewhere. Maintaining a uniform temperature is probably the single largest contributing factor for cloning success. If the temperature gets too hot, the clones may wilt and die before creating roots. If the temperature gets too cold, the clones may enter a state of suspended animation and never create the root systems they need to become individual plants. For growers using propagation trays for cloning, seedling heat mats are the best tools for maintaining the proper temperature.
Humidity is also a large contributing factor to successful cloning. Many cannabis varieties have higher cloning success rates with high humidity (80-99%) during the early stages of cloning. The marijuana cutting, once removed from the mother plant, has no root system to absorb moisture. It is, however, able to lose moisture through the surface of its leaves. This forces the cutting to rely heavily on the humidity in the surrounding air to maintain moisture, especially for the first few days. Humidity domes or humidity chambers are great ways for a grower to maintain a higher level of humidity during the initial stages of cloning. Most humidity domes are made to fit on the standard sized propagation tray and can be purchased for less than $10. It is a good idea to acclimate clones placed under a humidity dome to the ambient humidity after three to seven days. This can be done by taking off the humidity dome each day for a few minutes and then increasing the duration of removal time each day moving forward.
Another popular method for cloning marijuana is to use an aeroponic clone machine. An aeroponic clone machine is any cloning chamber that has an enclosed reservoir and sprays the stems of the cuttings directly with the cloning solution. Although each clone machine is a little different, most rely on a neoprene or plastic piece to hold the cutting in place and to “seal” the machine so water does not spray out of the top. Clone machines come in a wide variety of sizes and shapes and are powered by a submersible water pump or an external air pump. Although these machines differ in appearance, they are all based on the same concept: maximizing oxygen to the root zone. One of the main reasons these machines work so well is the perfect ratio of moisture to air surrounding the stem of the cutting.
Temperature can still affect success rates when using a clone machine. Clone machines are great in cooler locations, but in warmer conditions the submersible pump may heat the water beyond the desired range. A quick-fix solution is to connect a cycle timer to the pump and operate the pump a few minutes on and a few minutes off. As the timer cycles, the water cools during the off cycle and will hold less heat in comparison to the pump running continuously.
Many clone machines work well with straight water, but marijuana growers who want to speed up the rooting process generally add a rooting hormone or solution to the reservoir of the cloning machine.
Cleaning and sterilizing a clone machine is essential to maintaining high success rates. Many marijuana growers have great success the first few times using a clone machine, only to have their success rates drop off dramatically down the road. Hydrogen peroxide can be used to wipe down the entire clone machine after every use. It is important to soak the neoprene insert used to support the clones in a hydrogen peroxide or 10% bleach solution after every use as well. The neoprene inserts used in clone machines are very porous and may harbor many pathogens. For this reason, it is a good idea to get into the habit of replacing the neoprene inserts on a regular basis.
Tissue culture, in horticulture, refers to the replication of a plant from its cells or tissue which is grown in a nutrient culture medium under sterile conditions. Basically, tissue culture is like growing a plant in a petri dish from just the tiniest slice of tissue. A huge advantage of tissue culture is the ability to “clean” plant material of contaminates. In other words, a plant that has developed a disease or virus can still be propagated without bringing the pathogen along with it. This advantage alone provides an invaluable asset of preservation to modern horticulture.
Regardless of the cloning method used, many cannabis cultivators are using CO2 in the cloning stage. The biggest advantages of adding CO2 to the cloning stage are faster root initiation, reduced transpiration and an increased resistance to pathogenic molds, fungi and bacteria. There are a variety of ways to administer CO2 to cannabis clones. If using a compressed CO2 tank or CO2 burner, the grower should monitor the CO2 levels to make sure they are in check. For the cloning stage, CO2 levels between 1000-1300 ppm should be the maximum. Levels above this can be counterproductive as the available oxygen gets displaced by CO2. The roots (or potential roots) need some oxygen to develop and thrive. Using CO2 bags is another alternative.
Becoming proficient at cloning is the best way a marijuana grower can ensure a perpetual garden. By selecting a healthy and vibrant mother plant to take cuttings from, the grower only increases his or her chance of cloning success. Whether the grower uses a basic method, such as a propagation tray with a humidity dome, or a more sophisticated method, like a clone machine, close attention must be paid to the cloning environment. Put another way, the most important factors for cloning success are the temperature and humidity during the initial rooting stage.
With the aid of a rooting hormone and the proper atmospheric conditions, clones should begin to develop roots in about a week. Growers who utilize CO2 in the cloning stage could even have clones that develop roots in just a few days. Regardless of the method used, marijuana growers all have the same goal when it comes to cloning: to cultivate a heathy batch of young plants for the next grow cycle. A cannabis cultivator who can successfully clone will never have down time in his or her garden which equates to larger profits over time.
Eric Hopper is a Professional Marijuana Grower Senior Editor.