The post below comes from Aaron Anderson, a M.S. student in the OSU Department of Horticulture, and a member of the Garden Ecology Lab.
This past summer, we conducted the first field season of a study screening native plants for their attractiveness to pollinators and natural enemies. We selected 23 native Willamette Valley wildflower species based on drought tolerance, as well as four exotic garden species known to be attractive to bees: Nepeta cataria ‘Catnip’; Salvia elegans ‘Pineapple Sage’; Origanum vulgare ‘Italian’; Lavandula intermedia ‘Grosso’.
Table 1. Native plants selected for this study.
|Plant Species||Common Name||Life History||Bloom Color|
|Collinsia grandiflora||Giant blue eyed Mary||Annual||Blue|
|Gilia capitata||Globe gilia||Annual||Blue|
|Lupinus polycarpus||Miniature lupine||Annual||Purple/Blue|
|Madia elegans||Common madia||Annual||Yellow|
|Nemophila menziesii||Baby blue eyes||Annual||Blue/White|
|Eschscholzia californica||California Poppy||Annual||Orange|
|Helianthus annuus||Common sunflower||Annual||Yellow|
|Phacelia heterophylla||Varied-leaf phacelia||Annual||White|
|Acmispon (Lotus) parviflorus||Annual||White/Pink|
|Anaphalis margaritacea||Pearly everlasting||Perennial||White|
|Asclepias speciosa||Showy milkweed||Perennial||Pink/White|
|Aquilegia formosa||Western red columbine||Perennial||Red|
|Aster subspicatus||Douglas’ aster||Perennial||Purple|
|Camassia leichtlinii||Common camas||Perennial||Purple/White|
|Eriophyllum lanatum||Oregon sunshine||Perennial||Yellow|
|Fragaria vesca||Wild strawberry||Perennial||White|
|Iris tenax||Oregon iris||Perennial||Purple|
|Sedum oregonense||Cream Stonecrop||Perennial||Yellow|
|Sidalcea virgata||Rose Checkermallow||Perennial||Pink|
|Sisyrinchium idahoense||Blue-eyed grass||Perennial||Blue/Purple|
We planted them in meter squared plots at OSU’s North Willamette Research Center. Between April and October, we monitored floral visitation, sampled visiting insects using an “insect vacuum”, and tracked floral bloom.
With one season in the books, we have some purely anecdotal impressions of which wildflower species are the most attractive to bees. Goldenrod (Solidago canadensis) and Douglas aster (Symphyotrichum subspicatum) were both highly attractive to a wide diversity of native bees, as well as to a variety of beetles, bugs, and syrphid flies. As an added bonus, both these species had long bloom durations, providing habitat and colorful displays for significant portions of the summer. Annual flowers Clarkia amoena and Gilia capitata attracted a range of native bees; Clarkia was also visited by leafcutter bees for a different purpose – cutting circular petal slices to build nest cells with.
Results from this year need to be analyzed, and further research is needed to account for seasonal variability and to gather more data on floral visitors.
Additionally, w e will ask the public to rate the attractiveness of each of our study flower species in an effort to determine the best candidates for garden use. After a few more field seasons (and sorting lots of frozen insect samples!), the result of this study will be a pollinator planting list for home gardeners, as well as a pollinator and natural enemy friendly plant list for agricultural areas. These will help inform deliberate plantings that increase the habitat value of planted areas.