Thermopsis rhombifolia

Herbs dwarf and robust, 1.2–3 dm, glabrate to appressed-pubescent. Stems slender, erect or ascending, solitary or clustered, few-branched, from woody rootstock or rhizomes; branches ascending at 25–50º, weakly zigzag. Leaves: stipules persistent, ovate to widely ovate or elliptic to widely elliptic, 1–2.6 × 0.5–1.5(–2.2) cm, base cuneate to oblique, apex acute to obtuse, short-mucronate; petiole 0.8–2.2 cm; leaflet blades elliptic to obovate or narrowly elliptic, 1.7–3.3 × 0.6–2 cm, lateral veins 5–7 pairs, conspicuously net-veined abaxially, apex acute to obtuse, sometimes short-mucronate, surfaces appressed-pubescent to sparsely tomentose or glabrate abaxially, glabrous adaxially. Peduncles 1–4 cm; bracts deciduous, elliptic to obovate, 5–9 × 3–5 mm. Racemes 5–15-flowered, 4–12 cm; flowers in whorls of 2 or 3 or scattered. Pedicels 3–7 mm, glabrate to densely appressed-pubescent. Flowers 1.9–2.1 cm; calyx (6–)8–10(–12) × 4.5–6 mm at limb, lobes (3–)4–5 mm, equal to or shorter than tube; wing petals asymmetrically oblong to very widely ovate, keel petals asymmetrically oblong-widely elliptic; ovary glabrate to appressed-puberulent; ovules 12–14. Legumes divergent, strongly arcuate to annular, 3–7 × 0.4–0.7 cm, glabrate to sparsely tomentose. Seeds 2–10, brown, elliptic, 3.5–4 × 2.5 mm, beaked. 2n = 18.

Phenology: Flowering May–Jun.
Habitat: Xeric grasslands in deep alluvial soils and lower canyons, roadsides.
Elevation: 2000–3000.

Alta., B.C., Man., Ont., Sask., Colo., Mont., Nebr., N.Mex., N.Dak., Okla., S.Dak., Utah, Wis., Wyo.

Discussion

Selected References

None.

Lower Taxa