This locally competitive herb with spreading roots is known from the former midwestern tall-grass prairie (centered in Ill.) to lowlands around the central and southern Appalachians, but it is generally rare. It is most frequent in remnants of tall brushy grassland from e. Mo. to c. Ohio, but even there it is largely restricted to patches that have not been intensively farmed. It appears sensitive to continual effects of livestock. In Ky. it may have declined rapidly after settlement, since the only original record before 1900 is from Short (1840). He noted: "in thickets among the barrens; rather rare." [Rafinesque established the genus Orbexilum for this species but based on Nuttall's coll. from Mo., and he did not list it from Ky.] Most populations remain concentrated along old roadsides and fencerows on lowlands adjacent to the western edge of the Appalachians. The plant is similar in vegetative form to Desmodium cuspidatum, which occurs in similar habitat but across a wider range. However, O. onobrychis can form dense clonal patches up to 1-1.5 m tall, while D. cuspidatum generally has more scattered shorter stems. Its chemistry remains largely unknown, but probably includes furocoumarins such as psoralen; the foliage has a peculiar rubbery taste. Several insects are specialist feeders on this plant, and some are globally rare (A. Braun 1930; Harrison et al. 2014; L.D. Gibson, pers. comm.).