There has been increasing interest in providing pollinator habitat in urban landscapes. In particular, interest in native plants has increased, in part for their purported benefits to pollinators. However, in the Pacific Northwest the relative attractiveness of native plants to pollinators has not been tested. To address this, in 2017-2019 we screened 23 native Pacific Northwest wildflowers for their attractiveness to pollinators, natural enemies, and insect pests. Plants were selected based upon their potential ornamental use, as well as anecdotal reports of attractiveness to pollinators. We included four exotic comparators known to be attractive to pollinators. Each species was planted individually in replicated meter-squared plots. Between April and October, we monitored pollinator visits, floral-bloom phenology, and sampled insects, weekly.
To address acceptance for use in urban landscapes, we distributed two online surveys to gardeners. The first assessed how aesthetically pleasing they find these 27 plants and how likely they would be to utilize them in their home gardens. The second surveyed whether gardener preferences can be influenced by the ecological benefits that flower species provide, by asking respondents to rate top pollinator plants in the study before, and after, being shown facts about the ecological benefits each plant provides.
Results/Conclusions
The most attractive plants to bees varied each year, possibly due to differences in phenology and plant establishment. In 2017, four native wildflowers were the most attractive flowers for bees, followed by the exotic Nepeta cataria. In both 2018 and 2019, three of the six most attractive plants to bees were exotic species. However, this pattern was strongly driven by honey bee visitation. When we limited our analysis to native bee abundance, the six most attractive wildflowers were all native species. Across all three seasons, Eschscholzia californica, Phacelia heterophylla, Symphyotrichum subspicatum, and Gilia capitata were more attractive to wild bees than other flower species. Similarly, across all seasons native wildflowers attracted the highest wild bee species richness.
The gardener surveys revealed that several of the least visited flowers by bees were the most attractive to gardeners, and several of the flowers with the most bee visits were the least attractive to gardeners. However, the majority of the native study plants scored highly, showing a high potential level of acceptance by the public. We found that after education, respondents viewed flowers as 40%-80% more attractive, showing that the acceptance of native pollinator plantings to improve urban habitat may be increased with outreach.