Natives vs ‘nativar’: Do pollinators notice a difference?

Native plants are all the rage these days, and for good reason: They support regional wildlife, are adapted to the local climate and require minimal maintenance. But they don’t always fit seamlessly into a home garden setting. Although many wild plants are perfectly adapted to cultivation, natives are sometimes gangly, making them hard to weave into the average small plot.

Enter cultivars of native species — or “nativars” (a nonscientific term defined as a deliberately selected, crossbred or hybrid variation of a native species), the plant industry’s attempt to improve on nature. Given an aster with abundant quantities of sparkling blue flowers in fall, for example, they will imagine the package might look better in pink. It’s not just aesthetic changes, though; breeders also focus on creating plants that are more resistant to disease. But are these varieties equally attractive to the insects and birds who depend on them for sustenance? Researchers have been working to find the answer.

In 2011, Annie White was in the process of starting Nectar Landscape Design Studio when she hit a roadblock trying to find certain native species at local nurseries. To learn whether nativar substitutes would be equally efficient from a pollinator’s perspective, she dove into a Ph.D. research program. Working with the University of Vermont, White began a field study in two Vermont locations, collecting data until 2015. She planted 11 native species paired side by side with a cultivar and then observed approximately 8,000 visits from several pollinator groups — including bumblebees, honeybees, small dark bees, beetles/bugs, butterflies/moths, flies and wasps/ants.

Her findings? “Half the time there was a preference for the native species, and half the time there was no significant difference.” Only “Lavender Towers,” a cultivar of Culver’s root (Veronicastrum virginicum), outperformed the species in pollinator visitation. On the other hand, some cultivars were noticeably snubbed by pollinators. The pink-flowering aster “Alma Potschke” bombed. “Red Grape” tradescantia also got the thumbs down.

What drove the pollinators’ preferences? White suspected that nectar quantities might play a major role. Flower color and flowering time also could be factors.

Other researchers are also looking for answers. Mt. Cuba Center in Hockessin, Del., has a trial garden (open to the public) performing comparison tests of species native to the eastern United States and their cultivars. Primarily, their studies focus on garden worthiness. But thanks to the local Pollinator Watch Team, a group of 10 to 20 trained volunteers, recent trials also collect data on pollinator action. They confirmed that pollinators prefer the natives that they have co-evolved with. “The species are always the gold standard,” says Sam Hoadley, the center’s manager of horticultural research.

In some cases, though, pollinators did gravitate to the cultivars. A trial with beebalm (monarda) found that the bright red flowering nativar Monarda didyma, “Jacob Cline,” outperformed the species in hummingbird visits, 273 to 22. Meanwhile, the pale mauve nativar Monarda fistulosa, “Claire Grace,” also outperformed the species in moth and butterfly visits. Another surprise nativar standout was Phlox paniculata, “Jeana,” which outperformed the species “by a huge margin,” Hoadley says.

Flowering time can impact pollinator preferences. Although most nativars overlap with the species, that isn’t always the case. Some have an entirely different blooming window. Hoadley also says that management issues, such as pruning, can put any plant out of sync with its pollinators. “Delayed blooming can make them inaccessible, especially to specialist insects,” he says. And specialist insects that depend on one plant species for their survival tend to pay the price when things go out of sync. “There’s a lot of moving parts to consider,” Hoadley says.

Jen Hayes, a graduate research assistant, has been conducting a similar study at Oregon State University. She planted seven native species beside their corresponding cultivars and observed the reactions of bees, butterflies and syrphid flies over three years. Data is still being analyzed, but Hayes’s findings are similar to those of the other studies: Pollinators generally prefer the native species, and those plants also attract more specialist bees and more diverse pollinators.

All studies also confirmed what gardeners have long suspected — that the closer a nativar is to the original species, the greater the pull. Significantly altered flowers, including double echinaceas (“Pink Double Delight” in White’s study, for example) with petals in place of reproductive parts, only confuse pollinators.

Changes in a plant’s size and leaf color, on the other hand, don’t seem to affect pollinators’ interest, according to studies at Mt. Cuba. Varieties with chartreuse or variegated leaves, or more compact plants, typically performed just as well as the native plant, although caterpillar activity on shrub cultivars with red and purple leaves is still being studied.

Nativars generally scored relatively well, but there’s also the future to consider. If we are to keep plant and their corresponding insect populations healthy and thriving, genetic diversity should inform our choices. A native species has the greatest genetic diversity to create progeny that will survive stress, especially against the challenges of climate change. When gardeners shop local and hunt down nurseries that collect seeds of native plants from the nearby region, the resulting plants will have the suite of characteristics adapted to suit the local conditions. Nativars, with less genetic diversity, don’t have that edge. For example, in White’s Vermont studies, several nativars failed to survive bitter winters.

Even so, we shouldn’t entirely dismiss nativars; they do fill a niche. They act as a kind of introduction to the native realm for gardeners, particularly those in urban areas or with small spaces who want to make an environmental impact with less-than-ideal growing conditions. This is particularly true of plants (such as echinaceas) that are readily available at local nurseries.

Nobody should feel compelled to be a purist, Hoadley says. “Often, nativars inspire people to get started with native plants, bringing them into the conversation while being confident that they are doing something good.”