139. Eriogonum robustum Greene, Bull. Calif. Acad. Sci. 1: 126. 1885.
Altered andesite wild buckwheat
Eriogonum lobbii Torrey & A. Gray var. robustum (Greene) M. E. Jones
Herbs, erect, matted, 0.5-3 × 1-2 dm, tomentose to floccose. Stems: caudex absent; aerial flowering stems erect or nearly so, stout, solid, not fistulose, usually arising directly from a taproot, 0.5-1.2(-1.6) dm, tomentose to floccose. Leaves basal, in well-defined rosettes; petiole 1-4(-5.5) cm, tomentose to floccose; blade ovate to obovate, 2.5-4(-5) × 1.6-2.5(-3.5) cm, densely white- to grayish- or reddish-tomentose abaxially, less so to floccose or glabrous and greenish adaxially, margins entire, plane. Inflorescences 2-umbellate, 5-10 × 5-10 cm; branches tomentose to floccose; bracts 3-5 at proximal node, leaflike, 1.5-2.5(-3.5) × 0.3-0,8(-1) cm, sometimes absent immediately below involucre. Involucres 1 per node, campanulate, 8-11(-13) × 8-12 mm, thinly tomentose to lanate; teeth 6-10, usually lobelike, mostly reflexed, 2-6 mm. Flowers 7-9 mm, including 0.1-0.4 mm stipelike base; perianth creamy yellow to pale yellowish, glabrous; tepals monomorphic, oblong-obovate; stamens exserted, 7-9 mm; filaments pilose proximally. Achenes light brown to brown, 6-8 mm, glabrous.
Flowering Jun-Aug. Heavy clayey slopes, montane and subalpine conifer woodlands; of conservation concern; 1300-2000(-2500) m; Nev.
Eriogonum robustum is restricted primarily to altered andesite soils in west-central Nevada, essentially at the confluence of Carson City, Lyon, Storey, and Washoe counties. There, due to the unusual soil, the plants typically occur in areas without sagebrush but among conifer species usually found at higher elevations. The species is cultivated infrequently and is a food plant for the intermediate dotted-blue butterfly (Euphilotes intermedia).
Kuyper, K. F., U. Yandell, and R. S. Nowak. 1997. On the taxonomic status of Eriogonum robustum (Polygonaceae), a rare endemic in western Nevada. Great Basin Naturalist 57: 1-10.