One crisp, fall day, you wake up deciding you simply must plant a Ceanothus in your garden. So, off you go to your local, native plant nursery, heading straight for the Ceanothus. As you browse, you’re surprised by how many different varieties there are for sale, some with embarrassingly hokey nicknames like “Blue Jeans” and “Frosty Dawn.” (And who the hell are “Ray Hartman” and “Joyce Coulter?”) Understandably, you begin to wonder, “What are all these plants, exactly?”
Good question. The answer is, they’re cultivars.
Welcome to the cult.
Most native plant cultivars (or “nativars” as they’re apparently being called these days) begin as unique specimens observed in the wild that are “selected” for uniquely desirable and/or dependable characteristics such as growth or flowering habit. Contrary to a common misconception, while some native cultivars may have been “tweaked” after selection, the vast majority are not horticulturally cultivated hybrids. They’re mostly “discovered,” just as they are, like an old-school Hollywood movie star plucked from obscurity by some sharp-eyed agent at Schwab’s Drugstore. (Except in this case, the agent is probably some nerdy botanist in a Tilley hat.) But unlike the one-of-a-kind Veronica Lake or James Dean, cultivars are reproduced asexually, ad infinitum. In other words, they’re clones.
The end result is a seemingly endless stream of horticultural carbon copies
That Foothill Penstemon ‘Margarita BOP’ you put in the ground last fall, for instance, is a cultivar. It’s a product of asexual or vegetative propagation, meaning it started life as a cutting. As a result, it has the exact genetic profile of every other ‘Margarita BOP’ in the world, down to its last strand of DNA. ‘Margarita BOP’ is popular for its uniquely floriferous habit and the tolerance it demonstrates for “typical garden conditions” – characteristics it may not necessarily share with non-cultivar specimens of Penstemon heterophyllus (or the “species,” as non-cultivars are known). But the seeds of your ‘Margarita BOP,’ should they germinate, will not necessarily grow up to be a Penstemon with the same characteristics as the mother plant that produced them. That’s because when plants grow from open-pollinated seed, some genetic alteration necessarily takes place. So, if you want those same, subjectively desirable BOP traits every time, the plant must be propagated from cuttings. The end result is a seemingly endless stream of horticultural carbon copies.
LOOKS AREN’T EVERYTHING
Given the growing number and popularity of native cultivars, a conscientious native gardener might be forgiven for asking: what is the larger environmental impact of cloning an individual plant on an industrial scale, ad infinitum? Globally speaking, is it a good thing or a bad thing?
As usual, the answer lies somewhere in between, and the space separating “global” from “local” isn’t as wide as it might appear. In my opinion, there’s nothing essentially “bad,” about any one cultivar, and generally speaking, the use of cultivars has its place within the constellation of native plant gardening practices. But it’s critical to note that cultivars are almost exclusively selected by the horticultural trade for aesthetic reasons. When it comes to promoting biodiversity, however, opting for a popular cultivar over the straight species may not be the best choice.
There is mounting evidence that pollinators most often prefer the straight species over a cultivar in the same genus
“Biodiversity” is a word you hear a lot these days, but what does it actually mean, at least in this context? Well, imagine the 6,500 plant species native to the California Floristic Province reduced to a hundred or so species, and further imagine that these remaining species are all genetically identical to one another within their respective genus (a plant’s “surname”). That’s the opposite of biodiversity. An over-reliance on cultivars results in our native gardens becoming less genetically distinct from one another. Less genetic distinction necessarily results in lowered species resilience. Lowered species resilience can lead to the collapse of ecosystems and is, perhaps, the primary negative effect of biodiversity loss.
While a mass extinction event stemming from the overuse of cultivars is more than unlikely, there is, perhaps, a more compelling argument to be made for limiting them in order to promote biodiversity in your own native garden: the mounting evidence that pollinators most often prefer the straight species over a cultivar in the same genus. A lot of this has to do with a given plant’s level of “floral reward” – the amount of nectar and pollen available at any given time of the day – and with the sensitivities of pollinating insects to that plant’s particular appearance and rhythms – in other words, to the complex relationships governing the interactions between plants and pollinators. (It should be pointed out that there are a number of cultivars that appear to be more appealing to pollinators than the species, so while the general principle may be widely applicable, the attractiveness of each cultivar to its pollinators should ideally be evaluated on a case-by-case basis. See the Xerces Society’s “Picking Plants for Pollinators: The Cultivar Conundrum” for a more detailed discussion of these issues.)
While cultivars may have a role to play, here in the LANPS garden, we try to plant the straight species whenever possible. On those relatively rare occasions when we do plant a cultivar, it has to satisfy at least one of the following criteria: 1) there is a very specific reason for needing to know, in advance, how the plant will perform in a cultivated landscape; 2) the species just isn’t available and we don’t have the patience to either plant it from seed or wait until it appears on the inventory list of a local native plant nursery – someday.
Ironically, if and when you’ve decided to rely less on cultivars in your garden (or, at least, to be more discriminating when it comes to using them), yet another challenge awaits you: it can actually be quite difficult, if not impossible to find the damn species for sale, even at nurseries that specialize in California native plants. A glance at their inventory will usually tell you that a substantial percentage, if not the majority of certain plants within a given genus on the list are cultivars. Take Frangula californica or Coffeeberry, as just one example. Most of the inventory is likely going to be made up of cultivars like ‘Eve Case,’ ‘Mound St. Bruno’ or ‘Leatherleaf,’ all of which are clones. Oftentimes, the straight species, whose characteristics will be much less predictable, isn’t even offered. Luckily, however, despite the understandable financial incentive behind the marketing of cultivars, we’re now seeing the species being offered more frequently at many of these same nurseries.
So, before you fall for the undeniable charms of ‘John Dourley’ (Arctostaphylos), ‘Allen Chickering’ (Saliva), or ‘Bruce Dickinson’ (Eriogonum), consider enhancing the biodiversity of your own garden and giving your resident pollinators a boost by planting the species when you can: a non-cultivar, grown from open-pollinated seed.