Herbage bright green (under vestiture). Stems clustered from root-crown or subterranean to superficial caudex, decumbent (with ascending tips), (8)10–40(–50) cm. Leaves 3.5–13(–18) cm; leaflets (11–)15–29(–31), blades oblanceolate, elliptic, oblong-elliptic, narrowly obovate-cuneate, obovate or suborbiculate, 3–19(–22) mm, apex acute or obtuse. Peduncles (1.5–)2–6(–10) cm. Racemes (5–)7–15(–35)-flowered; axis 1–3.5(–14) cm in fruit. Pedicels 2.7–4.5 mm. Flowers: calyx (6.7–)7.7–11.3(–14) mm, strigu­lose, pilosulous, or ascending-pilose, hairs mixed black and white or all black, tube (5.2–)5.8–7.8(–8.6) mm, lobes (1.3–)1.7–4.2(–5.8) mm; corolla pink- or blue-purple; banner (16–)16.5–23.5(–25) × (7–)8–12.5 mm. Legumes globose or plumply ovoid-oblong or obovoid-oblong, 15–27 × 12–25 mm. Seeds 52–68. 2n = 22.

Phenology: Flowering Mar–Jul.
Habitat: Prairies, rolling plains, old pastures, roadsides, railroad rights-of-way, on calcar­eous stony hillsides, in open oak thickets.
Elevation: 200–1200(–1800) m.

Distribution

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Alta., B.C., Man., Sask., Ark., Colo., Iowa, Kans., Minn., Mo., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Wis., Wyo.

Discussion

Diversity in the widely distributed var. crassicarpus was discussed in detail by R. C. Barneby (1964). The plants in fruit, with the upper side suffused with red or red-purple, are truly beautiful and remarkable, supporting in their very appearance the designation of ground­plum. The legumes vary from globose to ellipsoid or quadrate, but the apex in all cases is abruptly acu­minate. The legumes are frequently broader than long (S. L. Welsh 1960). This is truly a plant of the prairies and plains of low to moderate elevations, a component of shortgrass to tallgrass prairies, whose total extent has been impacted by development of much of its habitat for growth of grains mainly.

Selected References

None.

Lower Taxa

None.