CORVALLIS, Ore. — Planting native plants is a popular way to support pollinators like bees, butterflies and other beneficial insects.
But when shopping for native plants, gardeners often come across cultivars — named varieties selected or bred for traits such as different flower colors, larger blooms, compact size or longer bloom periods.
“We found that the development of native cultivars can change traits that matter to bees, even when breeders were not intentionally selecting for nectar or pollen. Plants that stayed closer to the wild-type phenotype tended to support bee communities that were more functionally rich.”
These plants may look different from the wild-type native species they came from, raising a common question: Do they provide the same value to pollinators?
Research from Oregon State University suggests the answer is often no, especially for bees.
In the latest published study from her dissertation research, Jen Hayes, a postdoctoral scholar at Oregon State, examined whether native plant cultivars differ from wild native plants not just in pollinator visits, but in floral traits that shape how bees use flowers.
The study, published in the journal Environmental Entomology, found that most cultivars differed from their native counterparts in ways that could matter to pollinators, including flower color, size, bloom timing, nectar and pollen.
The researchers also found that nine of the 11 cultivars they studied had bee communities that differed from those found on the native plants they came from. In many cases, cultivars also supported a narrower range of bee types.
“We found that the development of native cultivars can change traits that matter to bees, even when breeders were not intentionally selecting for nectar or pollen,” Hayes said. “Plants that stayed closer to the wild-type phenotype tended to support bee communities that were more functionally rich.”
The study was conducted over four years at Oregon State University’s Oak Creek Center for Urban Horticulture in Corvallis. Hayes and colleagues in the OSU Garden Ecology Lab compared five Pacific Northwest native plant species and 11 cultivars, measuring floral traits and collecting bee data to better understand how plant breeding may affect plant-pollinator relationships.
It is the second study from the project published in the journal Environmental Entomology. The first, published in February 2025, found that pollinator visitation varied by plant and pollinator group, and that native plants were more often favored than cultivars when differences in visitation occurred. The new study goes further by asking why those differences may happen.
Looking beyond visitation
Past studies on native plants and cultivars have produced mixed results, Hayes said. One reason may be that many focused mainly on visitation counts rather than looking at the flower traits and bee traits that shape those interactions.
In the latest study, researchers measured bloom timing, floral density, plant height, flower size, flower color, nectar volume, nectar sugar content and pollen nutrition. They then examined the bee communities found on each plant, including differences in bee species and functional traits such as body size, tongue length and diet breadth.
These traits matter because not all bees use flowers the same way. Some are generalists, while others rely on a narrower set of plants. Some can access deep or complex flowers better than others.
A planting that supports a wider range of bee types may provide greater ecological value than one that mainly attracts a few abundant species.
Among the study’s findings, some cultivars had less nectar, lower sugar content or different pollen nutrition than the native plants they were derived from. Those changes were likely unintended side effects of selecting for ornamental traits rather than direct breeding for floral rewards.
Not all cultivars perform the same
The results were not all or nothing.
The researchers found that cultivars with traits closer to those found in wild populations tended to perform better for bees than more heavily modified cultivars. In some cases, minimally developed cultivars supported bee communities more like those of the native species.
One example was a white-flowered California poppy cultivar, which was the only cultivar in the study that did not have a significantly different bee community from its native counterpart.
The study also found that cultivars of Douglas aster, which were selected from wild-collected seed and represent less dramatic changes from the straight species, retained many associations with specialist bees and other functional bee traits seen on the native plant.
“The cultivars we used represent a spectrum,” Hayes said. “Some were minimally selected, while others were more modified through hybridization or ornamental breeding. That degree of change appears to matter.”
A practical message for gardeners
Hayes said the findings should not be interpreted as a blanket rejection of cultivars. Plant breeding can provide important benefits, such as disease resistance or traits that help plants succeed in landscapes.
But for gardeners whose main goal is to support pollinators, the study suggests that straight native species are usually the best choice. When cultivars are used, those that remain closest to the appearance and function of wild native plants are more likely to provide similar benefits.
“There is intrinsic value to planting native plants in the landscape,” Hayes said. “And if the goal is to maximize support for pollinators, especially a diversity of bee species, native plants are the safest choice.”
Hayes’ co-authors on the studies included: Gail Langellotto, Nicole Bell, Lincoln Best, Svea Bruslind, Devon Johnson, Kailey Legier, Mallory Mead, Tyler Spofford, Priyadarshini Chakrabarti and Lauren Baugus.
The research was funded by grants from the Native Plant Society of Oregon, the Garden Club of America, and donations to the Oregon Garden Research Fund by members of the Garden Ecology League.
Previously titled Native plants attract more pollinators than cultivars in OSU study
