110. Eriogonum siskiyouense Small, Bull. Torrey Bot. Club. 25: 44. 1898. (as siskiyouensis).
Siskiyou wild buckwheat
Eriogonum ursinum S. Watson var. siskiyouense (Small) S. Stokes
Herbs, spreading, matted, 0.5-2 × 1-5 dm, glabrate or glabrous. Stems: caudex spreading; aerial flowering stems erect, slender, solid, not fistulose, arising at nodes of caudex branches and at distal nodes of short, non-flowering aerial branches, 0.5-1.5(-2) dm, usually glabrous, with a whorl of 2-4 leaflike bracts ca. midlength, similar to leaf blade, 0.3-0.5 × 0.1-0.2 cm. Leaves in dense compact basal rosettes; petiole 0.2-0.6 cm, glabrate or glabrous; blade spatulate to round, (0.3-)0.5-0.8 × (0.2-)0.3-0.5(-0.7) cm, densely white to thinly tomentose abaxially, sparsely floccose to glabrate and green or olive green adaxially, rarely glabrous on both surfaces, margins entire, plane. Inflorescences capitate, rarely umbellate, 0.8-1.5 cm wide or 1-2 × 1-3 cm; branches usually glabrate; bracts absent immediately below involucre. Involucres 1 per node, turbinate-campanulate to campanulate, (3-)3.5-4 × 4-6 mm, arachnoid-tomentose; teeth 6-10, lobelike, reflexed, (2-)2.5-3.5 mm. Flowers (4-)4.5-6 mm, including 0.6-1 mm stipelike base; perianth sulphur yellow, glabrous; tepals monomorphic, oblong; stamens exserted, 3.5-5 mm; filaments pilose proximally. Achenes light brown, 4.5-5 mm, glabrous.
Flowering Jul-Sep. Gravelly serpentine slopes and outcrops, manzanita communities, montane conifer woodlands; 1600-2800 m; Calif.
Eriogonum siskiyouense is restricted to the ridge system that extends from the Scott Mountain area to the Mt. Eddy region of Siskiyou and Trinity counties. The vast majority of individuals in a population have a single involucre atop each flowering stem, but at lower elevations and in somewhat more protected sites the inflorescence may be umbellate. The Siskiyou wild buckwheat does well in cultivation if its soil requirements are fulfilled.