Native plants and native cultivars: Understanding pollinator preference for native plants and their cultivated counterparts in the Pacific Northwest

Native cultivars present a paradox for ecologically-minded gardeners: growing interest in native plants is largely related to their benefits to pollinators, yet many native plants found at nurseries may be significantly altered, compared to wild genotypes. The goals of our research were to identify potential differences in pollinator preference for wild type natives or cultivars, and to understand what floral traits plant breeding impacts. Over three field seasons (2020-2022), we vacuum-sampled and conducted 5-minute observations on insect pollinators visiting five species of Pacific Northwest native plants (Achillea millefolium, Aquilegia formosa, Clarkia amoena, Eschscholzia californica, and Symphyotrichum subspicatum) and one to three associated cultivars. We hypothesized that pollinator preference for native status (natives or cultivars) would vary by plant species group, and altered plant traits (via selections and/or breeding) may be associated with changes in visitation. In most native-cultivar comparisons, pollinator taxa exhibited no preference for either plant type. In significant comparisons, native plants were preferred 82% of the time, with long-horned bees, flower flies, and butterflies preferring native plants 100% of the time. S. subspicatum was the only species where cultivar preference occurred, for all pollinators, all bees, and bumble bees. Detailed measurements of plant traits may help identify which ornamental characteristics influence pollinator visitation to native plants and native cultivars, which is the focus of our current work. Though there is no trend across all plant and pollinator groups, we recommend wild-type native plants for conservation and pollinator gardens, to ensure specialist pollinators can meet their nutritional requirements.