Senna hebecarpa aka American Senna

Senna hebecarpa is a perennial in the pea family. Its common names include American senna and wild senna. Its native range spans southeastern Canada and the central and eastern United States. It grows along riverbanks, in damp woods, and in meadows. It also grows in pastures, roadsides, and other disturbed ground. Open sites help it avoid shade from trees and shrubs.

Plants reach 4–6 feet (1.2–1.8 m) tall in gardens. They spread 3–4 feet (0.9–1.2 m) wide. Growth is upright, though the whole plant can look rounded. Stout, pale green stems have some hairs near their tops. The leaves grow alternately along the stems. Each pinnate leaf has five to ten pairs of leaflets. These gray-green leaflets have smooth edges and pointed tips. Small stipules at the leaf stalk base soon fall off. The plant sheds its leaves as the season ends.

Yellow flowers form racemes or branched panicles above the leaves. Each flower has five petals and ten dark brown stamens. The blooms lack the shape of many pea-family flowers. Their petals fade toward white with age. North Carolina State places flowering in mid- to late summer. Chicago Botanic Garden lists blooms from July through October. Flat pods turn dark brown as they mature. Each pod holds ten to eighteen seeds in separate sections. The pods stay into winter and add interest after flowering. Their weight can bend the stems.

Full sun gives the best bloom, though partial shade works. Rich, moist loam suits the plant well. It also accepts sandy or rocky ground and brief floods. Established plants can withstand drought. The sources list USDA zones 4–9 and 5–9. Care needs are low, and growth is moderate. Rich, damp soil can produce tall stems that need support. Plants grow from seed or root divisions. Removing seed heads helps limit new seedlings in the garden.

American senna suits borders, meadows, and butterfly gardens. Bumblebees gather pollen, while several sulphur butterflies use it as a host. Their caterpillars eat leaves and flower buds. Birds, including bobwhites, grouse, and turkeys, eat the seeds. North Carolina State reports no other serious insect problems. Chicago Botanic Garden describes slight toxicity to humans and deer. Reported medicinal uses include laxative use of leaves and seeds. These uses do not establish that the plant is safe to eat.