Herbs annual, 10–50 cm, gla­brous. Stems erect, dichoto­mously branched. Leaves pal­mate; stipules lanceolate, 0.4–1.2 cm, margins lacerate, apex subulate; petiole 0.5–4 cm; petiolules to 0.5 mm; leaflets 3, blades linear, oblong, oblanceolate, or elliptic, 0.5–2.5 × 0.1–0.5 cm, base cuneate, veins fine or moderately thickened, margins entire, spinulose, or dentate, apex rounded or truncate, mucronate, surfaces glabrous. Peduncles 2.5–7.5 cm. Inflorescences axillary or terminal, 3–15-flowered, obconic, 0.3–1.2 × 0.3–0.8 cm; involucres flattened to bowl-shaped, 1–2 mm, when folded, not hiding flowers except proximally, incised 4/5–9/10 their length, lobes lanceolate-subulate. Pedicels erect, 0.5–2 mm; bracteoles absent. Flowers 11–16 mm; calyx campanulate, slit between adaxial lobes, 4–5 mm, glabrous, veins 10, tube 2.5–5.2 mm, lobes triangular-subulate, 3-fid or shouldered below apex, orifice open; corolla lavender with white tips, keel petals purple, 6–8 mm, banner narrowly ovate-oblong, 6–8 × 2 mm, apex narrowly rounded, erose. Legumes sessile, oblong, 2.1–3.2 mm. Seeds 1 or 2 (or 3), reddish brown, mottled, lenticular or reniform, 1.2–1.3 mm, smooth. 2n = 16.

Phenology: Flowering Mar–Jul.
Habitat: Stream banks, grassy, rocky slopes, meadows, fields.
Elevation: 0–1100 m.

Distribution

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B.C., Calif., Oreg., Wash.

Discussion

Trifolium oliganthum is relatively common through­out much of its range in California; it is found in a few scattered sites northward into Oregon, Washington, and British Columbia. Even though it closely resembles T. variegatum, it is placed near T. bifidum in molecular studies (N. W. Ellison et al. 2006).

Trifolium hexanthum Greene ex A. Heller, which pertains here, is not a validly published name.

Selected References

None.

Lower Taxa

None.