Herbs annual, 2–100 cm, resin­ous stipitate-glandular. Stems erect or ascending, branched. Leaves palmate; stipules ovate, 1–1.5 cm, sheathing, margins deeply lacerate, apex acuminate; petiole 1.5–10 cm; petiolules to 0.5 mm; leaflets 3, blades elliptic, lance­olate, oblanceolate, rhombic, or obovate, 1.5–4 × 0.3–1.7 cm, base cuneate, veins thickened, margins coarsely spinulose-serrate, apex acute, mucronate, surfaces glandular. Peduncles 3–15 cm, glandular. Inflorescences axillary or terminal, 10–50-flowered, globose or ovoid, 1–3.5 × 1–3 cm; involucres flattened or bowl-shaped, 3–8 mm, when folded, not hiding flowers except proximally, incised 1/4–1/3 their length. Pedicels erect, 1 mm; bracteoles absent. Flowers 13–20 mm; calyx tubular-campanulate, slit between adaxial lobes, 10–13 mm, glandular, veins 20+, tube 5–7 mm, lobes unequal, narrowly triangular or lanceolate-subulate, usually entire, rarely 3-fid or shouldered below apex, orifice open; corolla white or pale pinkish with dark purple spot, 10–18 mm, banner broadly elliptic, 10–18 × 2–4 mm, apex blunt. Legumes obovoid, 3.5–4 mm. Seeds 1 or 2, brown, mottled, ellipsoid or mitten-shaped, 2.5 mm, smooth. 2n = 16.

Phenology: Flowering Apr–Jul.
Habitat: Moist swales, creek bottoms.
Elevation: 0–1600 m.

Distribution

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Calif., Oreg., Mexico (Baja California, Sinaloa).

Discussion

Trifolium obtusiflorum is much less common than the similar T. willdenovii, occurring in moist areas in cismontane California and north into Oregon (W. L. Jepson [1923–1925]). It is easy to distinguish from T. willdenovii by its glandularity, which causes fresh specimens to be sticky to the touch.

Selected References

None.

Lower Taxa

None.