Herbs annual, 5–40 cm, pubescent. Stems erect, branched from base. Leaves palmate; stipules elliptic-ovate, 0.6–1 cm, margins entire, toothed, or remotely lobed, ciliate, apex acuminate; petiole 0.5–7 cm; petiolules 1 mm; leaflets 3, blades obovate or elliptic, 0.5–2 × 0.2–1 cm, base cuneate, veins obscure or slightly thickened, margins serrate, apex acute or obtuse, often retuse, surfaces pubescent. Peduncles 0.5–10 cm. Inflorescences axillary or terminal, 25–50-flowered, ovoid-ellipsoid, 1–1.8 × 0.8–1.5 cm; involucres absent. Pedicels absent; bracteoles absent. Flowers 6–9 mm; calyx campanulate, 6–8 mm, densely pubescent, veins 10 (additional faint veins sometimes present), tube 1–2 mm, lobes unequal, narrowly triangular, subulate, sinuses rounded, lobes divergent, orifice open; corolla white with purple tips, 4–6 mm, banner narrowly elliptic, 6–7 × 2 mm, apex acute, slightly erose. Legumes broadly ellipsoid, 2.8–3.2 mm. Seeds 1 (or 2), yellow or brown, often red-mottled, ellipsoid, 2–2.6 mm, smooth, glossy. 2n = 16.

Phenology: Flowering Apr–May.
Habitat: Grassy foothills and valleys.
Elevation: 0–2100 m.

Distribution

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Ariz., Calif., Oreg., Wash., Mexico (Baja California).

Discussion

Trifolium albopurpureum is a widespread member of a closely allied group of species, including T. amoenum, T. dichotomum, and T. columbinum, that intergrade to varying degrees and may co-occur in some popula­tions. The great similarity among these species has led to a maddening array of synonyms as new suites of spe­cies have been recognized and various new combinations have been made. In spite of the resultant confusion, these species are relatively distinct and are differentiated on the following characters: inflorescences generally greater than 3 cm diam. (T. amoenum) versus less than 2.5 cm diam. in the others; corollas usually 8–12 mm with calyx lobes 2–3 times the tube (T. dichotomum), versus corollas usually 5–8.5 mm with calyx lobes 3–6 times the tube; calyces 8–12+ mm with lobes exceeding the corollas by 3–6 mm (T. columbinum), versus calyces 4–9 mm with lobes equaling the corollas or exceeding them by 1.5–2 mm (D. Isely 1998; M. A. Vincent and Isely 2012).

Trifolium albopurpureum is widespread in California, northward through Oregon in coastal counties, and with scattered populations known from Washington and Arizona.

Selected References

None.

Lower Taxa

None.