Plant of the Week: Wild Senna

Senna hebecarpa, also known as wild senna or American senna, is a perennial legume found in North America. This plant prefers sun or light shade with medium water requirements. Senna thrives in clay moist soils and tolerates periodic flooding, making it common in Madison’s stormwater land.

Wild senna in direct sun will grow flowers fuller and more numerous than senna grown in the shade.  The flowers on wild senna are clusters of light yellow to orange flowers.  As with many other legumes, wild senna plants initially send their energy into their root system, therefore the top of the plant will be slow to develop. This initial slow top growth in the first two years is normal, especially in the early spring. Once plants have become established they will grow vigorously and are very drought tolerant. 

Wild senna is a hardy plant with relatively few problems. This species is easy to grow and maintain with moderate levels of nitrogen, potassium and phosphorous. Due to the substantial taproot of this plant it is difficult to transplant or divide. This species is best planted in the spring or early fall from container stock to ensure success. The leaves and pods of the wild senna contain compounds called anthraquinones, which are powerful laxatives.  For this reason, cattle and other herbivores avoid grazing the plants.