A common notion amongst the Cannabis growing community is the idea that when we propagate plants asexually, or make clones, that a clone of a clone of a clone eventually will lose vigor due a degradation of the plant's genetic integrity. Many growers, including growers with years of experience, report the effect of vigor loss on their crops after several batches of cuttings from the same variety have been put through flowering. This leads to the assumption by many that the strain has permanently lost vigor because the genetics have “mutated”, “worn out” or “slowed down.”
Many other growers who have been successfully growing the same variety for years do not ascribe to this theory. In short, the environment that a plant is grown in can only influence the expression of an organism's genetics; it cannot degrade or influence the actual “blueprint” of the genetics themselves. Loss of momentum in Cannabis crops can occur for a number of reasons, but it is important to note that even when a plant does not express its genetics to the full potential that a grower once saw, the blueprint itself has not changed.
Let's consider this example: A worker in a factory accidentally gets his arm caught in one of the machines and has to get it amputated (just bear with me). After recovering from the loss of his arm, he gets his wife pregnant and 9 months later, she gives birth to his offspring. How many arms will the kid have? Well, two, of course. The fact that an organism experiences events that change its physical makeup does not change the DNA in its cells. The blueprint is still encoded to build the organism with 2 arms. For examples from the plant world, consider that the 'Peace' variety of Rose was bred in the late 1930s, the 'Delicious' variety of apple has been around since 1870 and the 'Bartlett' pear has been around since 1770. None of these plants has the capability to grow one individual for that length of time, yet when propagated asexually, these plants seem to last forever.
Genotype vs. Phenotype
From Wikipedia.org, “Genotype is an organism's full hereditary information, even if not expressed...The genotype represents its exact genetic makeup – the particular set of genes it possesses...Phenotype is an organism's actual observed properties.” Phenotype refers to the specific expression of an organism's genetic makeup under a certain set of environmental conditions. Phenotype is also a common vernacular term in the Cannabis growing community, often shortened to just “pheno”, which growers use to refer to different individuals from the same generation of seeds. The use of the word in this case is actually a misnomer, since phenotype refers to separate expressions of the same genetic individual in differing environments. If we're talking about separate seeds, then the differences expressed between them is actually a distinction of genotype as they are all separate individuals.
To understand the term phenotype, we have to consider the example of identical twins. Identical twins in the human world would be roughly equivalent to a seed that splits into 2 identical seeds. This doesn't happen with Cannabis, so even plants that resemble each other to a large degree are still only as closely related as paternal twins – which have an even greater degree of variation. So 2 seeds from the same female plant can only be as closely related as paternal twins and have at least as much variation between them as sisters would. We've all met someone who looks so similar to their sibling; it's obvious when you see them together. Conversely, there are occasions where if the sibling relationship wasn't pointed out to you, you might never know the 2 individuals were related.
Often, when growers report a visible change in their crop over time, it's due to a change in the environment, which subsequently affects that plant's phenotype, or genetic expression. Even in the case of identical human twins, where the genotype is identical between two individuals, there are differences in the expression of those genetics according to the environment. They even have unique fingerprints despite the matching genetic blueprints. The bottom line is that every genetic individual can look different under different environmental conditions. That's why the same strain grown by different growers can look so different. But those changes over time are not the result of the genes changing – they're a result of the environment changing the genes expression.
What about mutations?
Simply put, mutations are random changes in the genetic blueprint of an organism. Over the years, I have heard many stories of strains that “mutated” to have different characteristics. In most, if not all, of these cases it was simply a loss of momentum or the result of a grower seeing a different phenotypic expression of the plant that resulted in this diagnosis. As far as mutations go, there are 2 primary things for growers to consider. The first thing you need to know about mutations is that they almost never happen. In statistical terms, genetic mutations are far less common than 1 in a million, yet I hear them reported far more often than that. The second thing to consider about mutations is that they almost never benefit the organism. So even when that 1-in-a-million event occurs, it usually kills or injures the organism affected. There are millions of base pairs of genetic information contained in the DNA of Cannabis plants. It's comparable to the millions of lines of code contained in a computer's operating system. A mutation in the DNA of a plant is kind of like going into your computer's operating system and randomly changing a line of code. Yes, there is some possibility that the change you made could make something work better, but the odds are definitely against it. So if it's not mutations changing the plant, what causes the perceived loss of vigor?
Strong Plants Make Strong Stems Make Strong Plants Again
I use the word “momentum” throughout my CannAcademy curriculum because it highlights how cumulative the process of gaining vigor is to a plant. Many growers believe that vigor is largely controlled by genetics and, while that is true to a certain degree, it is not the whole story. Vigor does not occur right away, it builds slowly and picks up speed as the plant develops. In the case of growing Cannabis via asexual propagation, the plants can lose a significant amount of momentum when they are cloned. It’s essentially a surgery for the stem being propagated. That's why growers need to focus on taking the most vigorous growth from the parent plants and create a stress-free cloning process. It helps maintain the momentum that the plant has hopefully already established.
Imagine 2 patients (cuttings) undergoing the same surgery (cloning process) from 2 different doctors (growers). Patient A is in a generally unhealthy condition, at a hospital with bad equipment and his surgeon isn't the best, either. Patient B is the picture of health, at the finest hospital and has the best surgeon around. Obviously, the recovery time for Patient B is going to be far less than for Patient A. Now add to this analogy that an aggressive flowering cycle for Cannabis plants is like running a marathon for a person. If that marathon is scheduled for just a few weeks after the surgery, then you don't want to waste lots of veg time on a recovery period. It's imperative to start healthy and avoid stress for the best results later.
When growing Cannabis, momentum can be lost quickly, yet can take a long time to regain it once lost. When growers report a slow but consistent decline in the vigor of their gardens, I look at the source of the plant material that starts the garden. Typically, I find problems with either the vegetative area or the cloning process. Because momentum is a cumulative effect, a flowering garden can only produce buds as good as the plant materials that went into it. The largest cutting in a tray becomes the largest vegetative plant, which inevitably produces the largest buds in the flowering garden. So then the question becomes – How can we always start with the most vigorous plants possible?
A Cut Above
There are 2 primary sources to acquire the stems to make cuttings. The first method is to use “mother stock” - plants that are grown in a vegetative state indefinitely in order to constantly produce new growth tips for cloning. The other method is to take vegetative shoots off the undergrowth of plants that are being vegged to make a flowering crop. In many cases of reported vigor loss, the gardens use these undergrowth cuttings from the bottom of each canopy to start the next crop. Because these shoots are coming from light deprived areas of the canopy where growers would otherwise have to remove the growth in flowering anyway, they are not nearly as vigorous as cuttings taken from the top of the canopy. If these low vigor cuttings are then turned into their own canopy, which produces slightly less vigorous plants than the previous time, then you can see how the momentum is slowly but consistently diminishing.
When growers use mother stock for their cuttings, they can cut the largest top branches to make into cuttings. However, mother stock plants can also lose vigor over time simply because they are often not given an optimum environment. Medical Cannabis typically requires 50 - 90 days of cropping time, but cuttings root in just 7–14 days. Because of this, mothers are frequently kept off to the side of the vegetative garden where they receive less
light and grow more slowly. Many growers suspend the growth like this because there's no rush to take the cuttings. Unfortunately, the growth that will be the next crop is losing momentum already. Ideally, those mothers should be given the same abundant amount of light and other resources in order to produce the largest, healthiest branches possible. If the mothers are given a quality environment and cared for properly, they should produce healthy cuttings for a long time – sometimes for years off the same mother stock. Eventually, that individual plant will show signs of decline, but again, the blueprint in the cells isn't being altered. If a cutting is taken from a declining mother and given proper care and an extended stay in a good environment, then that momentum can be re-established and new, healthy mother stock can be re-started. I've personally seen examples of strains brought back from the edge of death to later become the mother of thousands of vigorous cuttings. In the most extreme cases of battered, unhealthy plants, it wasn't an overnight process to re-establish that vigor, but it's certainly possible if placed in the right environment for a long enough period.
The Importance of Seeds vs. The Cost of Selection
While asexual propagation will always be the backbone of medical Cannabis production, those cuttings have to come from somewhere. No matter how many awesome strains you grow, the demand for new and unique varieties will always be present. The problem with seeds is that most of them will not make the cut. That's the way it should be. In order to get a good new variety, growers need to start with seeds from a reputable background or seed company. Then, they need to sprout as many of those seeds as possible. Luther Burbank is regarded as one of the greatest plant breeders of all time, although his selection process was remarkably simple. He sprouted as many seeds at a time as possible – hundreds at a time or more - in order to select from the largest population base. Then he'd walk the rows of plants every day and look for that outstanding unique individual or trait. Because Cannabis seeds are sold in relatively small increments compared to other garden plants, it can be difficult to get a large number of plants to choose from. Plus, each plant should be cloned (and carefully labeled) before being flowered, so growers really need 2 plants worth of space for every plant being looked at.
When you consider all the costs associated with indoor cultivation, growing out 10 seeds can be an expensive proposition since they will take up 10 spots in the vegetative garden and 10 spots in flowering. As the plants are sexed, many of them will be removed from the garden along with the corresponding vegetative copy. Of the females that develop, many of them can be good, but are often not outstanding. Getting an amazing strain is a process of time, labor, expertise and luck. If the grower doesn't have an extensive amount of experience, they may select a variety based on only a few variables (like yield) without regard for others (like disease resistance or medicinal properties). Also, the desire to simply have a unique strain of their own may motivate growers to keep substandard varieties when they'd be better off continuing their process of selection. Growing out seeds can be a great way to find that awesome new variety that no one else has, but it can also be a very expensive and time consuming process. Be patient and don't allocate more resources to selection flowering than you can afford to. That having been said, small gardens built for seed selection can be an excellent long-term investment for experienced growers and breeders.
When outstanding new varieties are discovered, growers face the problem of how closely to hold on to the strain. Many of the best strains of Cannabis are never released to the market as cuttings in order to give exclusivity to the product that it produces. While this is understandable considering the size of investment toward developing the strain, it also keeps all the eggs in one basket. Raids, bugs, equipment failure, and other bad day scenarios can now take out more than just a crop – they can erase a strain that took a lot of work to breed and/or select for. Having a trusted grower friends that understand the importance of keeping strains both alive and in limited release can help to keep the strain in more than one garden. Then, if you have a bad day and the cops destroy all your plants (they like to ignore clearly displayed Medical Marijuana postings until after the plants have been stomped into the ground...“oh, whoops..”), at least you can call up your friend and start over later with your beloved strain. I've heard many stories about genetic changes in Cannabis plants over the years. Often, the story about the strain losing vigor over time parallels another story of a garden whose environment is constantly changing. A variety that looks great during a chilly winter may look completely different when grown during the hot days of summer. Again, that's a result of different “genetic expressions” or phenotypes from the same plant. The genes still contain the same blueprint. It can be an easy answer for frustrated growers to sum up a garden's problems by believing the problem is in the plant itself. Often, changing conditions or a lack of maintenance in the garden can be the cause of a subtle but frustrating loss of vigor over time. So before you toss out that world-class variety of Cannabis simply because it's not doing what it used to, try starting some new mother stock and really focus your resources on them. Momentum is not always quick to come back, but under the right conditions it is inevitable.
(Growers Grove writer Jade Kine is a former greenhouse manager for the medical Cannabis industry with over a million plants worth of experience. He is also the founder of CannAcademy [www.CannAcademy.com], a trade school dedicated solely to horticultural training for growers. Got a grow question for Jade? Drop him a line at
and find his complete bio and previous articles at www.JadeKine.com Facebook/Twitter: