Wild senna is a tall, upright perennial reaching 4–6 feet in height and about 3 feet across. Stems are coarse and unbranched, supporting compound, pinnate leaves with 4–8 pairs of ovate to elliptical leaflets. The foliage is a dull to medium green and gives the plant a distinctly shrub‑like profile in midsummer.
Bright yellow flowers appear in mid to late summer in axillary racemes. Each bloom is roughly ¾ inch across, with five petals and a cluster of prominent stamens. The flowers produce pollen but no nectar, making them especially attractive to bumblebees and solitary bees that specialize in pollen collection.
Wild senna grows in full sun to light shade and favors moist, well‑drained soils, though it tolerates sandy or rocky substrates. In Wisconsin it occurs along woodland edges, thickets, open fields, riverbanks, and wet prairies. The plant serves as a larval host for several sulphur butterflies, and its seeds are eaten by upland gamebirds such as quail and dove.
Sources:
Wisconsin State Herbarium — Senna marilandica
Illinois Wildflowers — Wild Senna
Missouri Botanical Garden — Senna marilandica Plant Details
USDA Plants Database — Senna marilandica Overview Minnesota Wildflowers — Senna marilandica (Wild Senna)