a cultivar is a sort of functional grouping of plants based upon the fact that they fit a certain criterion—the trait or traits the breeder was looking for in selecting the cultivar in the first place.

To obtain and stably maintain important traits in some plants, it is necessary to identify a single plant with those traits and then make exact genetic copies, via cloning.  In such cases, the cultivar can only be one that is genotypically uniform.  All members of the cultivar are genetically identical.  This is the case with cultivars or “varieties” of grapevines and fruit trees, for example.  They are asexually propagated and, to put them into the context of other posts on this site, are protected by plant patents.  To read more about plant patents, click here.

However, in other plants, the traits that matter in defining the cultivated variety—the cultivar—can be heritable via sexual reproduction.  In those cases, essentially all of the seeds produced by a certain event, whether that event is a self-pollination, an open pollination, an F1 hybridization of specific parents, etc., produce plants that display the cultivar-defining traits.

Of course, this makes sense because it is utterly impractical to propagate some plants asexually, and yet these seed-propagated plants are bred, selected, and cultivated to obtain certain desirable traits.  Familiar examples of seed-propagated plants are the grains like wheat and rice.  IP protection for most seed-propagated plants is available in the U.S. through the USDA Plant Variety Protection (PVP) system.  While USDA PVP protection is not currently available for Cannabis cultivars, this post explains what can be done to protect seed-propagated cultivars, cost-effectively, with U.S. patents.

Some plants, like Cannabis and turfgrasses, are propagated both via seeds and by cloning.  For example, some Cannabis cultivars have traits that are uniform enough to be seed-propagated and other Cannabis cultivars require clonal propagation to maintain their key traits.  This fact demonstrates why it was important to come up with a an inclusive term, like cultivar, that would cover both situations—cultivated varieties phenotypically “uniform enough” for commercial purposes, whether those varieties happened to be genotypically uniform or not.  However the cultivation and selection is done, and whatever traits collectively are important enough to define the cultivated variety, that set of traits, uniformly inherited, defines the cultivar.

Varieties Can Be Naturally-Occurring

Now on to the term “variety,” which is conceptually part of the more preferred term “cultivar.”  Variety is just a less-specific term, because there can be naturally-occurring varieties as well as cultivated varieties.  Nonetheless, it is often used interchangeably with cultivar, probably because in the context of commercial plants and plant breeding, it is implicit that a variety under discussion would be a cultivated one.  Even official legislative documents like the Plant Variety Protection Act use the term.  So it’s not an incorrect term, just more inclusive than would be ideal, inasmuch as it brings in certain varieties that were of natural origin and, therefore, should not be the subject of intellectual-property protection.  The plant varieties produced by nature are and always should remain part of the public domain.

Strain Has No Accepted Meaning

What about the term “strain,” and where does it fit?  The term strain appears to be used most often and most correctly in connection with microbes and viruses, and more informally in reference to plants and rodents.  In plants it has no official meaning but generally applies to the group of offspring that are descended from a modified plant.  I think the main reason people tend to use the term in some situations is because they may receive a sample—some seeds or an individual plant—from someone else.  They maintain it through some generations and may keep using the same name as the strain they were given.  Or they may give it a new name to reflect any changes that they selected for or that they may just have observed while in their care.  Since there is either no need or no formal process for naming or registering this particular genetic line, the strain name they give it is enough.  So they refer to it as a strain, just to avoid appearing to elevate the name to some higher level of official evaluation or importance.  It seems to be essentially a default status.  Kind of a common-law variety or cultivar, so to speak.

This usage appears much more common in Cannabis than in other plants I have worked with.  My guess is that this is because Cannabis breeders have not been as involved in the out-in-the-open cultivar development and naming and intellectual-property protection process as breeders of other plants.  So maybe it will take a while for the Cannabis community to move from “strain” to “cultivar,” or maybe it will remain a part of the idiom of the industry.

Regardless of whether there is ever a uniform adoption of the term “cultivar” in the Cannabis industry, it’s at least interesting (well, maybe only to me) to understand the extent to which the terms “cultivar,” “variety,” and “strain” overlap, how their usage may have originated, and why the usage might persist.  And, now that you have read all the way to end of this post, welcome to the terminology-geek club.