Southern Senna

Senna marilandica

Southern senna is a bold back-of-border perennial that covers itself in bright yellow flowers in midsummer. the kind of plant that stops garden visitors in their tracks in July. The large, pinnate leaves are lush and tropical-looking, and the canary-yellow blooms open in clusters all up the stem over a long season. Bumblebees visit almost exclusively for the pollen, using a technique called 'buzz pollination' where they vibrate the anthers at exactly the right frequency to release it. It's a host plant for sulfur butterflies whose caterpillars feed on the leaves. The flat seed pods that follow turn dark and persist on the stems through winter, providing structural interest and seeds for birds. This is a nitrogen-fixing plant that improves soil over time without any help from you.