American River sulphur flower

Eriogonum polyanthum Bentham in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 12. 1856; E. umbellatum Torrey subsp. polyanthum (Bentham) S. Stokes

Shrubs, round, rather open, 4-10 × 5-10 dm. Aerial flowering stems erect, 1-2 dm, floccose, without one or more leaflike bracts ca. midlength. Leaves in rather open, terminal rosettes; blade oblanceolate to narrowly elliptic, 1-3 × 0.3-1(-1.3) cm, densely white-tomentose abaxially, thinly floccose or glabrous and light green adaxially, margins plane. Inflorescences umbellate or compound-umbellate, branched 1-2(-3) times; branches thinly floccose or glabrous, occasionally central branch seemingly with a whorl of bracts ca. midlength; involucral tubes 2.5-4 mm, floccose, lobes 2-3.5 mm. Flowers 4-7 mm; perianth bright yellow.

Flowering Jun-Sep. Serpentine flats and slopes, oak and montane conifer woodlands; 800-1500 m; Calif.

The inflorescences of var. polyanthum are commonly compound-umbellate, but plants with reduced yet bracteated inflorescences do occur. Those with a reduced inflorescence technically consist of a long (6-10 cm), central, bractless peduncle and two lateral branches (3-4 cm), with each of the latter bearing a peduncle (3-6 cm). Such branches seem to have a whorl of leaflike bracts, but actually the bracts are positioned between the branch and involucres (technically at the base of the peduncle) and thus are like other members of the genus.

The name var. polyanthum has been misapplied in California to plants here attributed to var. modocense and var. dumosum.