Trifolium howellii

Herbs perennial, 30–100 cm, glabrous. Stems erect, fistulose, unbranched or branched distally. Leaves palmate; stipules ovate, 1.5–4.5 cm, margins usually entire, sometimes lobed, apex acuminate; petiole 0.5–20 cm; petiolules 1–1.5 mm; leaflets 3, blades ovate, elliptic, or rhombic, 3.5–9.5 × 2.3–5 cm, base cuneate, veins obscure, margins ± serrate, apex acute, rounded, or obtuse, surfaces glabrous. Peduncles 3–11 cm. Inflorescences terminal or axillary, 20–70-flowered, globose or ellipsoid, 2.5–4 × 2–2.5 cm, rachis prolonged beyond flowers, undivided or forked, often bearing sterile flower buds distally; involucres absent. Pedicels strongly reflexed in fruit, 1 mm; bracteoles minute, blunt or acute, membranous. Flowers 10–14 mm; calyx campanulate, gibbous, 4–5.5 mm, glabrous, veins 10, tube 2–2.5 mm, lobes subequal, linear-lanceolate, orifice open; corolla white, lemon yellow, or greenish yellow, 11–12 mm, banner elliptic-oblong, 11–12 × 4–5 mm, apex obtuse. Legumes oblong or clavate, 4–5 mm. Seeds 1–3, reddish black or brown, angular, mitten-shaped, 2.5 mm, smooth or slightly roughened, dull.

Phenology: Flowering Jun–Jul.
Habitat: Wet stream banks, wet meadows, flood plains, shady woodlands, springs, thickets.
Elevation: 800–2000 m.

Calif., Oreg.

Discussion

Trifolium howellii is known from Del Norte, Humboldt, Siskiyou, and Trinity counties in California, and Clackamas, Douglas, Jackson, Josephine, Klamath, Lane, and Linn counties in Oregon (J. M. Gillett 1972). It has some of the largest leaves of any species of Trifolium in North America.

Selected References

None.

Lower Taxa