cultivar [ KUHL-tuh-vahr ] noun: a plant originating and persisting under cultivation
nativar [ NEY-tuh-vahr ] noun: cultivar of a native plant species
variety [ vuh–RAHY-i-tee ] noun: a naturally occurring variation of a species that can reproduce its own type; a taxonomic rank below subspecies and above form
Imagine yourself at a plant sale looking at plant labels with the terms: native, nativar, variety, cultivar, and hybrid. Would you understand the differences and does it matter?
You probably know that a native plant species is one that has evolved naturally in your particular region, and that a hybrid is the product of two or more plants of different kinds. But the terms variety and cultivar are often used interchangeably.
That ambiguity dates back about 270 years to the “father of modern taxonomy,” Carl Linnaeus, who talked about cultivated varieties (Spooner et al. 2003). Fortunately, botanical nonmenclature, which was codified in the early 1950s, provides some clarity.
A variety is a naturally occurring plant that shares most of the characteristics of the species but exhibits some different and stable trait(s) that it can pass on to its offspring. Just because a variety occurs naturally, though, does not mean that it is native. Even if its species is native to your area, a particular variety may not be.
A cultivar is a species manipulated by humans to enhance its vigor or appearance (e.g., improve disease/pest resistance, make it more compact, or alter foliage or flower color or form). Cultivar names are usually surrounded by single quotes. Nativar is a term coined within the last decade—combining native cultivar—often used to promote the cultivars of native plants.
So now that you understand what these terms mean, let’s talk about why the type of plant you choose for your garden matters.
When we lose habitat to agriculture and residential and other human development, we lose native plants and the wildlife with which they have co-evolved. Globally, 40% of all insect species are in decline. In the United States and Canada, almost 3 billion wild birds (29% of the population) have been lost since 1970. Bucking this trend are waterfowl and waterbirds that inhabit wetlands. Their numbers have actually increased proving that concerted efforts and investment in wetland conservation over the last several decades have worked.
Every native plant garden established becomes part of a larger effort to support native pollinators and other wild animals and to preserve biodiversity. So, when investing in a plant, try to find a native species (or native variety)—one that has been locally grown and adapted—that will thrive on the site in which you wish to plant it.
So, what about cultivars and nativars? Humans often create cultivars to “improve” the look or salability of a plant, rather than considering its function in the ecosystem. Before investing in a culitivar/nativar, try to find out how it differs from the native species.
Value to Wildlife
Experiments on native woody plant cultivars have shown that insects were less likely to feed on the foliage of a cultivar bred to have red, blue, or purple leaves during the growing season rather than the green leaves of its parent or “straight” species (Baisden et al. 2018). Research has shown that for herbaceous plants, “the more manipulated the cultivars became, the less attractive they became to pollinators” (White 2013/2016). For example, insects and birds showed significantly less interest in the pom-pom-like double flowers of Echinacea purpurea ‘Pink Double Delight,’ in which extra petals replaced reproductive parts, than in the straight species, Echinacea purpurea (Mount Cuba Center 2018-2020). These types of cultivars appeal more to humans than to pollinators and other animals.
Left to right: Echinacea purpurea with eastern tiger swallowtail, and cultivars Echinacea purpurea ‘Magnus’ with sachem skipper and two-spotted bumble bee and Echinacea purpurea ‘Pink Double Delight.’
It would seem to make sense then, if we want to support pollinators, we should look for the cultivars with the highest pollinator appeal. Tests have been conducted on a number of cultivars and their straight species to count the number of pollinator visits to each. High pollinator appeal of a cultivar may be the result of the right combination of color, pattern, morphology, and habit. Or, increased pollinator visits to a cultivar may be the result of extending the number of weeks it blooms, so that it overlaps with the bloom time of other native plants with which the straight species does not normally compete. In either case, if the pollinator appeal is such that the pollinators devote more time to the cultivar and less to native species, then this can disrupt the ecological balance.
Long-term Benefits versus Risks to Natural Systems
Although research has shown that certain traits can diminish an insect’s interest in a particular cultivar, entomologists, botanists, and horticulturalists still debate what risks cultivars may pose to native habitats. Some believe that cultivars in urban/suburban pollinator gardens are unlikely to “threaten the vitality of a local ecosystem” (Oder 2021). But, cultivars do not exist in a vacuum. Even if you think your garden is isolated from natural habitats, pollen and seeds might be carried miles away by animals, wind, and water. Any cultivar that is not sterile has the potential of cross-pollinating its relative.
Left to right: Native species Coreopsis verticillata, sterile cultivar Coreopsis verticillata ‘Moonbeam,’ native species Eutrochium dubium, sterile cultivar Eutrochium dubium ‘Little Joe.’
Increasing a nativar’s vigor by improving disease resistance to a non-native invasive plant pathogen could be beneficial, especially if this resistance could be passed on to the native species under attack. But what if a nativar’s vigor was increased to such an extent that it outcompetes and eradicates neighboring species? If this trait were passed on to the wild relatives, it would put the ecosystem at risk. (Tangren 2023) There is always the possibility that instead of, or in addition to, the intended benefit of a cultivar, an unintended perverse result will ensue.
In theory, sterile nativars cannot cross-breed with their native relatives. Yet, there is the example of the infamous cultivar of non-native Pyrus calleryana (callery pear), the ‘Bradford’ pear. Although bred so it could not self-pollinate, horticulturalists eventually learned that it could cross-pollinate with the shoots of its rootstocks and with newer callery pear cultivars, turning what was promoted as a sterile cultivar into a highly invasive pest. According to the University of Maryland, no research has been conducted to discover how cross-pollination with fertile Mid-Atlantic nativars affects wild populations and their pollinators. “Plant populations and natural areas benefit from adaptive genetic diversity, not random genetic diversity” (Tangren 2019). In fact, there is enough concern worldwide about cross-pollination with cultivars that there are global efforts to preserve genetic diversity by seeking out, collecting, and storing in banks the seeds of wild plants that have evolved through natural selection over millions of years.
As with any investment, do your research before you lay out your money. A good rule of thumb for a gardener is: grow plants that you find aesthetically pleasing, that provide value to you and to wildlife, and that will not harm the ecosystem.
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References
Baisden EC. Tallamy DW. Narango DL. Boyle E. 2018. Do Cultivars of Native Plants Support Insect Herbivores? HortTechnology. 28(5). doi: 10.21273/HORTTECH03957-18
Echinacea for the Mid-Atlantic Region. 2018-2020. Trial Garden. Mt. Cuba Center.
Nicholson ME, Hawke RG. 1995. Rudbeckia for Cultivated Landscapes. Plant Evaluation Notes. Chicago Botanic Garden. Issue 8.
Oder T. 2021. Challenges with Cultivars. Mother Earth News.
Smith C, Oten K. 2022 Callery Pear: ‘Bradford’ and Other Varieties and Their Invasive Progeny. Invasive Forest Pests. North Carolina State Extension.
Spooner DM, Hetterscheid WLA, van den Berg RG, Brandenburg WA. 2003. Plant Nomenclature and Taxonomy: An Horticultural and Agronomic Perspective. Horticultural Reviews. Volume 28. Edited by Jules Janick. ISBN 0-471-21542-2.
Tangren S. Updated 2023. Cultivars of Native Plants. University of Maryland Extension.
White AS. From Nursery to Nature: Are native cultivars as valuable to pollinators as native species? Posted by pollinatorgardens February 8, 2013; updated 2016.
White AS. 2016. From Nursery to Nature: Evaluating Herbaceous Flowering Plants Versus Native Cultivars for Pollinator Habitat Restoration. PhD dissertation, University of Vermont.