Developing regionally-specific wildflower mixes for pollinator habitat restoration in farmland: Lessons from Michigan

Background/Question/Methods

Native bees provide valuable pollination services to a variety of food crops, but they face myriad challenges in simplified agricultural landscapes where diverse pollen and nectar resources are restricted, and where nesting sites may be limited. Provision of additional foraging and nesting habitat through the establishment of native wildflower plantings has the potential to significantly increase pollinator populations in and around restoration sites and may support greater yields of adjacent insect-pollinated crops. In order to ensure the effectiveness of pollinator habitat restoration efforts, regionally-appropriate seed mixes will need to be developed. Research in Michigan and elsewhere has evaluated specific forbs for pollinator attractiveness; however, a plant’s likelihood of attracting pollinators does not necessarily predict its viability under varying soil and climatic conditions, or when placed into a mix with other plant species. Seed mixes must include species that are both attractive to pollinators and capable of growing in a variety of conditions.

Five native wildflower seed mixes (basic and diverse annual mixes, basic and diverse perennial mixes, and an annual/perennial mix) were evaluated at three sites in western Michigan and compared to an unsown, weedy control and to flowering buckwheat (Fagopyrum esculentum), a common non-native cover crop in our region. Plots were evaluated for plant establishment, floral density, and the abundance and richness of bees and other flower visitors as well as other arthropods.

Results/Conclusions

Several native forb species consistently attracted a higher abundance and diversity of native bees and were chosen for inclusion in a seed mix intended for pollinator habitat restoration on fruit and vegetable farms in western Michigan. Annual and perennial mixes had similar floral density and area in the first year, but these were higher in perennial mixes than annual mixes by the second year. Native bees visited flowers in greater numbers in both perennial mixes than in the annual or annual/perennial mixes, largely due to highly attractive bee balm (Monarda fistulosa), black-eyed Susan (Rudbeckia hirta), and New England aster (Symphyotrichum novae-angliae).  Weedy volunteer species established in all plots except the flowering buckwheat, including several that contributed to overall pollinator attractiveness. Through this and related ongoing research projects, important lessons were learned regarding how best to restore and manage habitat for pollinators in the Midwest region of the United States.