Herbs annual, 7–30 cm, gla­brous. Stems erect or ascending, sparsely to much branched. Leaves palmate; stipules ovate-lanceolate, 1–1.5 cm, margins entire, apex acute-acuminate; petiole 8–12 cm; petiolules 1 mm; leaflets 3, blades oblance­olate or obovate, 2.8 × 1.9 cm, base cuneate, veins delicate, margins entire or shallowly dentate distally, lateral veins sometimes ending in a bristle, apex rounded to acute, surfaces glabrous. Peduncles 5–15 cm. Inflorescences axillary or terminal, 3–16-flowered, in 1–3 whorls, subglobose, 2–2.8 × 1.8–2.6 cm; involucres bowl-shaped, 6–15 mm, lobes 6–8, broadly lanceolate, margins entire, acuminate, apex 3–5-fid. Pedicels straight, 0.5–1 mm; bracteoles absent. Flowers 12–14 mm; calyx campanulate, 5–8 mm, gla­brous, veins 10, tube 2.5–4 mm, lobes 11–15, unequal, abaxial 3–5 forked, adaxial unbranched, orifice open; corolla creamy white to pinkish, 11–13 mm, banner ovate, inflated entire length in fruit, not distally twisted, 11–13 × 5–7 mm, apex rounded. Legumes ellipsoid, 5–6 mm. Seeds 1 or 2, gray-brown, black-mottled, sub­globose, 2.5 mm, smooth.

Phenology: Flowering Apr–May.
Habitat: Shallow, vernally wet depres­sions on volcanic flats, banks of watercourses flowing through open rocky grassland, transitional habitats with scattered chaparral and conifers.
Elevation: 300–800 m.

Distribution

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Calif.

Discussion

Trifolium piorkowskii is known only from Shasta County.

Selected References

None.

Lower Taxa

None.