Restricted to the northern and western counties where it is infrequent. It grows on very dry, sandy or gravelly soil and is found mostly in a prairie habitat along roadsides and in open woodlands that have recently invaded prairie areas. This is closely allied to Desmodium canadense and may be distinguished from it by the large, persistent stipules, in contrast with the narrow, deciduous ones of D. canadense, and by its inflorescence. D. illinoense usually has a long, terminal raceme, which is much longer than the branches of the panicle, while the inflorescence of D. canadense is more compact and usually composed of many racemes of nearly equal length, although the main axis is sometimes much longer.
Stem erect, 1-2 m, pubescent with hooked hairs, commonly with a single long terminal raceme or few-branched panicle; stipules ovate, acuminate, 10-15 mm; petioles much longer than the stalk of the terminal lfl; lfls lance-ovate, rough on both sides with hooked hairs, strongly reticulate beneath, the terminal one 6-10 cm; axis of the infl softly spreading-hairy as well as commonly with some hooked hairs; fls 8-10 mm, white, on pedicels 12-23 mm; stipe 2.5-5 mm; articles 2-5, 4.5-7 mm, with rounded margins. Rich prairie soil; s. Ont. to Wis. and Neb., s. to O., Okla., and n. Tex. July, Aug.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.