Strophostyles helvola is an annual, branching vine to 1 m long, twining in low vegetation.
Leaves alternate, 3-parted, somewhat ivy-like, leaflets 2-6 cm long, egg-shaped, often with side lobes, lateral margins often concave, sparsely hairy below.
Flowers pink-purple, eventually turning green, 0.8-1.4 cm long, pea-flower-shaped, standard folded over other petals, keel petal strongly curved into a beak, side petals shorter than keel; calyx nearly hairless, irregular, 4-lobed, lowest lobe longer than others; inflorescence of small, rather dense clusters on a stalk to 30 cm long; blooming June-Oct.
Fruit dry, hollow pods, cylindrical 4-9 cm long, sparsely hairy, splitting open to release seeds, the pod halves becoming coiling; seeds to 1 cm long, wooly.
Wetland status: FACU-.
Frequency in NYC: Infrequent.
Habitat: Open areas, mostly on dry, sandy soil.