Herbs perennial, 10–60 cm, villous. Stems erect, branched or unbranched. Leaves palmate; stipules linear, oblong, or ovate, 1.5–2.5 cm, margins entire or slightly serrulate, apex acute to acuminate; petiole 1–20 cm; petiolules to 0.5 mm; leaflets 3, blades linear, elliptic, oblong, or lanceolate-elliptic, often folded, falcate, 4–11 × 0.1–1.6 cm, base cuneate, veins thickened, margins denticulate, apex acute or acuminate, surfaces villous. Peduncles 2–6 cm. Inflorescences terminal, 70–80-flowered, spi­cate, ovoid to cylindric, 3–6 × 2.5–3 cm; involucres absent. Pedicels erect or absent, 0–0.5 mm; bracteoles absent. Flowers 17–18 mm; calyx campanulate, 5 mm, villous, veins 20, tube 2.5 mm, lobes subequal, subulate, straight, orifice open; corolla creamy white, keel petals crimson, 12–22 mm, banner oblong, 12–22 × 3–5 mm, apex acute; ovaries glabrous or pubescent distally. Legumes obovoid, 4–5 mm. Seeds 1–3, reddish brown or tan, ellipsoid, 1.8–2 mm, smooth, glossy. 2n = 32.

Distribution

nw United States.

Discussion

Subspecies 2 (2 in the flora).

J. M. Gillett (1972) stated that the leaflet width in the basal leaves is the best distinction between the two subspecies, which are geographically isolated.

Selected References

None.

Lower Taxa

Trifolium plumosum subsp. amplifolium, Trifolium plumosum subsp. plumosum

Key

1	Leaflet blades of basal leaves 0.2–0.5(–0.7) cm wide, apex acuminate; herbs 20–35 cm.	Trifolium plumosum subsp. plumosum
1	Leaflet blades of basal leaves (0.8–)0.9–1.6 cm wide, apex acute; herbs 10–60 cm.	Trifolium plumosum subsp. amplifolium