Synonyms: Hosackia pinnata, Lotus bicolor
Bog deer-vetch is a perennial wildflower with many erect to spreading stems from 15-60 cm long. The leaves are pinnately compound with 5-9 elliptic, oblong or obovate leaflets, each 1-2 cm long. The leaves are 4-8 cm long.
The flower heads are 3-to 12-flowered umbels. The flowers range from 10-15 mm long with yellow banner and keel and white wings. The calyx is tubular and 4-8 mm long with triangular-lanceolate teeth from 1/5-1/3 as long as the tube. The upper two calyx lobes are joined most of their length and are merely notched between them. The seed pods range from 3-6 mm in length and 1.5-2 mm wide with 8-20 seeds.
Bog deer-vetch is found growing in the slow moving water of streams that dry up by mid-summer.
Bog deer-vetch may be found from northwestern Washington south to central California and east along streams and lakes to Idaho.
In the Columbia River Gorge, it may be found between the elevations of 200'-2000' from Cape Horn east to the Klickitat River.