Adding to the uniqueness of Wild Senna, its flowers do not have nectaries to attract pollinators like that of other flowering plants. Even so, its pollen attracts bees in droves, particularly Bumblebees and Sweat Bees. According to a 2016 study conducted by Penn State, Picky eaters: Bumble bees prefer plants with nutrient-rich pollen, it was found that Wild Senna is a favorite of Bumblebees with high protein-to-lipid ratio pollen. When visiting, bees use buzz pollination to shake, rattle and roll the pollen onto their lower abdomen and legs. It’s a delightful sound and one that you need to experience! With declining bee populations worldwide, planting more Wild Senna is a great way to help our apian friends. Note: in addition to Wild Senna, other plants in this study ranked highly with our bee friends including Common Spiderwort and Culver’s Root – perennials native to Wisconsin!
For an added layer of protection, Wild Senna has secondary nectar sources that are separate from the flowers. Strategically positioned on the leaf stems near the primary plant stem and next to the flower buds, ants, parasitic wasps, and lady beetles are rewarded with nectar for protecting the plant against leaf-eating predators. Smart AND sneaky!
Wild Senna are a host plant for a variety of butterflies including the Orange-barred Sulphur (Phoebis philea), one of the largest Sulphurs in Wisconsin, and the Silver-Spotted Skipper (Epargyreus clarus). The Gorgone Checkerspot (Chlosyne gorgone), a Wisconsin Special Concern species, is attracted to the pollen of the Wild Senna. A rare migrant to Wisconsin, the Cloudless Sulphur butterfly prefers Wild Senna as it is one of their host plants. Larvae will eat both the leaves and flowers. The caterpillar will turn green when eating the leaves or pale yellow if eating the flowers.
Once flowering is complete, clusters of flat and long brown seeds resembling pea pods appear, providing food for game birds such as the Northern Bobwhite (Colinus virginianus), a quail of Special Concern in Wisconsin, as well as wild turkeys, and songbirds.