Get to Know Our Natives: Wild Senna (Cassia hebecarpa)
A Midwestern prairie native that is perfectly adapted to our growing conditions, Wild Senna has much to offer in the summer garden. Its feathery Mimosa-like leaves provide excellent foliage interest throughout the growing season. In fact, Cassia’s foliage alone would make it worthy of a spot in the garden. However, in addition to beautiful foliage Wild Senna also offers showy flowers & seed-heads and is an excellent pollinator plant. It thrives in full sun to partial shade and is adaptable to a range of soil conditions.
Wild Senna is a specimen-sized plant that will grow 4′-6′ tall in ideal conditions. We believe it deserves much wider use and urge you to consider it for a sunny site with space for a large, showy herbaceous perennial.
Bloom time is usually July through August. Cassia produces abundant small yellow pea-like flowers in clusters on the ends of the stems in summer.
The flowers are followed by clusters of slender, elongated green pea-like pods. These pods age to mahogany or chocolate brown and are quite decorative. Furthermore, they act as a food source for wild birds. Wild Senna will self-sow modestly.
Bees and other native pollinators LOVE Cassia! While the flowers themselves do not produce nectar, they are an excellent source of nutritious pollen and will be heavily visited throughout the bloom period. You will rarely see these flowers without beneficial insect visitors! Interestingly, Wild Senna produces nectar separate from its flowers in nodules along the stem. These extrafloral nectaries are a food source for native Lady Beetles, ants and beneficial parasitic wasps.
Wild Senna’s foliage and seeds contain compounds called anthraquinones. These compounds act as potent laxatives and discourage browsing by deer & rabbits. Native Americans utilized this plant for its laxative properties, and it continues to be used for that purpose in herbal medicine today.
Some caterpillars, though, have adapted to feeding on the foliage and are unaffected by these compounds. Included in this group is the Cloudless Sulphur Butterfly. Caterpillars of this species depend on Senna plants to survive and, as a result, this species even takes its name from this plant (Phoebis sennae).
by Zannah Crowe