Don’t Let the Term “Strain” Strain You

By Dale Hunt

Photo Credit: My 420 Tours – Image licensed under the Creative Commons Attribution-Share Alike 4.0 International license.


Several years ago, I was sharing drinks and conversation with some friends at a Cannabis industry meeting when the topic of correct terminology arose.  Specifically, this happened when I used the term “strain” in the way it is commonly used in reference to Cannabis.  A friend pointed out that this term was not ideal for professional conversations, especially conversations with scientists and businesspeople.  I was warned that these audiences may see such usage as imprecise, unsophisticated, and reflective of a lack of awareness of more proper terminology such as “variety” or “cultivar.”

At that time, I already had about two decades of experience doing patent work in plant genetics – mostly with fruits and flowers – so I was very familiar with “cultivar” and “variety” as accepted terms in plant breeding and patent-speak.  But I was newer to Cannabis conversations; I had adopted the vernacular of the industry and used the word “strain” the way most other people did.  So this conversation spurred me to do some thinking and a little research and led me to write a blog post on the topic.  To summarize that post, I explained that “cultivar” was the most correct term to use in reference to plants that result from breeding and selection; “variety” could also refer to naturally occurring groups of plants and was, therefore. a little less precise in reference to plants bred by people; and “strain” had no accepted meaning outside the context of microbes and viruses.

Now that some time has passed, and I have the benefit of countless additional conversations with people from all areas of the Cannabis community and industry, I have revised my prior thinking on this topic.  I see the traditional usage of “strain” in Cannabis vernacular as being generally consistent with the usage of the term in other fields of biology.  In fact, I think it is a more correct term for a selection that has been made from a breeding process.  This approach reflects a commendable acknowledgement of the fact that, in most cases, what people call strains would not be fully qualified to be called cultivars.

For something correctly to be called a cultivar, it must be substantially uniform and stable.  As anyone who has done much with Cannabis genetics is aware, finding a single plant with some desirable combination of traits is great, but that is usually an early stage in a much longer process.  To produce – from seeds – plants with that combination of traits, making the initial selection is usually followed by numerous additional steps (and years) of crosses, selections, and more crosses.  Eventually a group of plants can be produced that consistently and uniformly express the desired traits.  At the end of this process, when the breeder has a stable seed line, it is appropriate to call that line a cultivar.  To apply the term cultivar to any of the earlier stages would be incorrect or misleading, because it would imply a level of stability and uniformity that wouldn’t yet exist.

So what should we call that first selection, or any of the generations that come after it but that don’t qualify to be called a cultivar?  The traditional use of “strain” in this situation is perfect.  Yes, it’s an unusual usage scientifically because the usage is usually reserved for microorganisms.  But why is that the case?  With some important exceptions, new strains of microorganisms are not the result of intentional breeding and selection to the point of uniformity.  They are just identified based on a set of traits and then named.  Frankly, I think the use of “strain” among Cannabis breeders reflects a commendable acknowledgement that what they have, while it may be something interesting, may not be uniform or stable.

Of course, when a new strain is propagated by cloning, it’s very likely that the clones will be uniform.  Will they be stable, generation after generation?  Not always.  That is why it’s best to avoid taking clones of clones of clones (etc.) if mother plants from an earlier generation are still available for cloning.  Even with cloning, while we can usually expect uniformity, there’s no guarantee of stability; in fact, there’s a working assumption against stability, or nobody would worry about taking clones of clones of clones.

If a clonally propagated line is substantially stable, it is appropriate to call it a cultivar.  But, again, there is nothing wrong with calling it a strain, as a kind of admission that nobody really knows how stable it will be over numerous generations of cloning.

And this is why the term “strain” no longer strains me.