Flora of North America species comparison

glabrate or glabrous; rachis sparsely gland-dotted, sparsely puberulent or glabrous; leaflets (7–)9–13(–17), stipels acicular, 1.2–2.2 mm, petiolule 2–3(–4) mm, usually sparsely gland-dotted, rarely eglandular, pilosulous to glabrate or glabrous, blade broadly elliptic to broadly oblong, (12–)25–40(–70) × (9–)15–25(–35) mm, base round, margins flat, entire or slightly crenulate, apex often emarginate, sometimes round to truncate, surfaces gland-dotted, puberulent to glabrate or glabrous; midvein terminated by a swollen mucro, 0.2–0.6 mm. Racemes 1–4-branched, (8–)10–20 cm; rachis sparsely gland-dotted or eglandular, puberulent or glabrous; bracteoles narrowly oblong, 1–1.5 mm, glabrous except margin stiffly hairy. Pedicels 1–1.5 mm, eglandular, puberulent to glabrate or glabrous. Flowers: calyx tube narrowly conical to funnelform, 2.8–3.2 mm, distal 1/4 not obviously gland-dotted, puberulent to glabrate or glabrous; lobes mostly round, 0.4–0.9(–1.2) mm; banner purple, obcordate, 5–7.5 × 4.5–6 mm, not clawed, margins entire, apex emarginate; filaments 8–10 mm, connate basally 3–6 mm; anthers yellow; ovary usually glabrous. Legumes sessile, 7–9 × 3–4 mm, margins curved outward abaxially, straight or sharply bent adaxially, at least distal 1/2 gland-dotted, usually glabrous. Seeds dark brownish to blackish, 4–5 × 2.5–3 mm, smooth.

Amorpha ouachitensis is listed as a species of concern by the states of Arkansas and Oklahoma; it is in the Center for Plant Conservation’s National Collection of Endangered Plants.

(Discussion copyrighted by Flora of North America; reprinted with permission.)