Cannabis Cultivation: Seeds vs. Clones
Written on 26 September 2020
by Ruth Fisher, PhD
Cannabis plants are dioecious, that is, they are either male or female. Plant reproduction occurs naturally, when male plants pollinate female plants, causing female plants to produce seeds. New cannabis plants can thus be cultivated by collecting seeds from fertilized females and replanting them, or by buying seeds generated by someone else.
Alternatively, new cannabis plants can also be cultivated using cloning, a form of asexual reproduction. Clones are cuttings taken from a mother plant that are cultivated separately to generate a new plant. Whereas new plants cultivated from seeds carry genetics from both mothers and fathers, cloned offspring carry genetics only from mothers. That is, clones are genetically identical to mother plants.
Cannabis plants, then, can be cultivated either by using seeds or by using clones. Each method has its advantages and disadvantages; this analysis aggregates and compares reported plusses and minuses of each.
In keeping with the same approach I used to compare indoor and outdoor growing, I classify different aspects of the seed vs. clone comparisons into three categories: grow environment, quality of flower, and cost or effort required. Tables summarizing the advantages and disadvantages of each grow method are provided in Figures 1 and 2.
Grow Environment
Starting with the grow environment, seeds have greater shelf lives than clones. Seeds can be stored for months or years, while clones must be cultivated right away, or they will die.
Seeds are also free from pests, while clones may carry infestations from the mother plant.
Turnaround times, however, favor clones over seeds. Seeds take several weeks longer than clones to flower: seeds must germinate and grow to reach the same level of maturity that clones have already achieved.
Quality
Perhaps the most important advantage of using seeds rather than clones is the fact that plants grown from seeds have a taproot, while cloned plants do not. Having a taproot makes plants “infinitely more robust and have faster growth rates in most cases”:
Cannabis grown from seed has a taproot—a central root which is sent deep into the soil from which subsidiary roots grow.
When a cutting is taken from a cannabis plant, the cutting must develop a tangle of roots to funnel up moisture and nutrients. Clones lack a taproot and therefore are structurally (not genetically) distinct from cannabis grown from seed.
“The lack of a taproot definitely affects the vigor of a cloned plant when compared to the growth rate of a seed plant,” said Pace [Russell Pace III, President of the Cannabis Horticultural Association.]. “A seed plant will be infinitely more robust and have faster growth rates in most cases.”[1]
Lack of a taproot in clones is a contributing factor to clonal degradation, which, in turn, contributes to declining yields in clones from one generation to the next. [2]
Another advantage of seeds over clones is the large variety of seeds available. Seeds can be purchased from anywhere in the world and delivered to growers. The variety of clones, however, is limited to what’s available from local growers.
An essential factor for cultivating cannabis flower is using female plants, which yield the resin sought by flower growers. If growers use regular seeds, then only about half the resulting plants will be female, while the other half will be male. Male plants are actually a hazard to growers, since they may pollinate female plants, causing females to seed and reduce their resin yields. Using regular seeds is thus relatively costly to growers because they must germinate their seeds, wait several weeks until the sexual organs are visible, then remove any male plants. Growers who use seeds are thus left with only half the number of plants originally cultivated. On the other hand, growers looking to use seed have the option of purchasing feminized seed, which are seeds that have been engineered to produce only female plants. As Leafly[3] describes it,
Feminized seeds are produced by causing the monoecious, or hermaphrodite condition in a female cannabis plant. The resulting seeds are nearly identical to the self-pollinated—or “selfed”— female parent, as only one set of genes is present.
This is sometimes referred to as “cloning by seed” and will not produce any male plants.
The gender issue is much more straightforward when using clones: a clone taken from a female plant is guaranteed to be female.
The last issues that fall into the quality category are risk and replication. Seeds are much riskier than clones to the extent that (i) some seeds do not sprout, and/or (ii) the quality of plants grown from a given batch of seeds varies due to differences in genetics. There is much less risk and more consistency in this regard from clones, whose yields will replicate those of the mother plants.
Cost/Effort
Comparing purchase costs and cultivation effort of clones versus seeds is difficult. If a grower already has her own plants, she can pollinate them to produce a limitless supply of seeds for free. If she has to purchase them, however, and she wants good quality plants, then the seeds may be expensive. Similarly, if a grower already has his own plants, he can clone them for free. Otherwise, he has to find an available mother plant from which to purchase clones.
Finally, it appears that clones are easier to grow than seeds, being less delicate and generally requiring less skill to cultivate than seeds.
Figure 1 summarizes the respective advantages and disadvantages of seeds and clones.
Figure 1
Conclusion
Figure 2 provides a more succinct summary of the information presented in Figure 1.
Figure 2
It looks like growers who are in it for the long haul, who seek variety and vigor in their flower, and who are willing to invest in the skills needed to handle seeds might do better with seeds. In contrast, growers who are interested in quicker turnarounds and less fuss might do better with clones.
Most growers prefer clones to seeds. As Emma Stone from Leafly puts it,
Cannabis cloning represents an incontestably straightforward way of getting identical cannabis. What’s more, it’s currently the most dominant method of cultivating cannabis. In a commercial context where consumers demand consistency, it’s a gift.
References
[1] Stone, E. Does cloning ruin cannabis strains over time? Leafly. Retrieved from https://www.leafly.com/news/growing/does-cloning-ruin-cannabis-strains
[2] Stone, E. Does cloning ruin cannabis strains over time? Leafly. Retrieved from https://www.leafly.com/news/growing/does-cloning-ruin-cannabis-strains
[3] Leafly Staff. Cannabis seeds 101: A guide for growers. Leafly. Retrieved from https://www.leafly.com/news/growing/cannabis-seeds-101-all-you-need-to-know-and-mor