Crosby's wild buckwheat

Eriogonum capistratum Reveal; E. capistratum var. muhlickii Reveal; E. capistratum var. welshii Reveal; E. meledonum Reveal; E. ochrocephalum S. Watson var. alexanderae Reveal; E. verrucosum Reveal

Herbs, matted, scapose, 0.05-1.5(-2) × (0.1-)1-3 dm, floccose to tomentose or glabrous, sometimes glandular, greenish or grayish. Stems mat-ted, with persistent leaf bases, up to 5 height of plant; caudex stems matted; aerial flowering stems scapelike, weakly erect to erect, slender, solid, not fistulose, 0.02-1.5(-1.8) dm, floccose to tomentose or glabrous, occasionally also or only sparsely to densely glandular.  Leaves basal, fasciculate in terminal tufts; petiole 0.2-3(-3.5) cm, tomentose, infrequently glandular; blade oblanceolate to spatulate or elliptic to obovate or ovate, (0.5-)1-2(-3) × 0.2-1(-1.5) cm, densely white- or grayish-tomentose on both surfaces, sometimes less and greenish white adaxially, margins plane.  Inflorescences capitate, 0.7-1.5 cm; branches absent; bracts 3, narrowly triangular to triangular, scalelike, 1-3 mm. Peduncles absent. Involucres (3-)5-8 per cluster, turbinate to campanulate, (1.5-)2-5(-5.5) × 2-4(-4.5) mm, rigid or membranous, tomentose to floccose, occasionally glabrous except for floccose teeth, rarely sparsely pilose and glandular; teeth 5-7, erect to spreading or reflexed, 0.5-1.5 mm. Flowers 1.5-3.5(-4) mm, glabrous or occasionally minutely glandular, pustulose in some; perianth yellow to pale yellow or, rarely, cream; tepals connate proximal 4- 3, monomorphic, oblong to oblong-obovate; stamens exserted, 1.5-4 mm; filaments glabrous or sparsely pilose proximally. Achenes light brown, 2-4 mm, glabrous or sometimes with minute bristles on beak. 2n = 40.

Flowering May-Aug. White tuffaceous shale volcanic outcrops, metamorphic rock outcrops, or basaltic or granitic sandy flats, washes, slopes, and ridges, saltbush and sagebrush or high-elevation sagebrush to alpine tundra communities, juniper or montane conifer woodlands; (1200-)1400-3100; Idaho, Mont., Nev., Oreg.

Eriogonum crosbyae, as now defined, is widely scattered in the valley bottoms and foothills, and atop several mountain ranges of central Idaho (Blaine, Butte, Camas, Custer, and Lemhi counties) and in western Montana (Deer Lodge and Ravalli counties). It is disjunct to southwestern Idaho (Owyhee Mountains, Owyhee County), southeastern Oregon (Guano and Coleman valleys, Harney County, and Fish Fin Rim, Lake County), and in northwestern Nevada (Washoe and Humboldt counties south through Douglas, Lyon, and Pershing counties to Mineral County). It also occus in the Marys River Peak area of Elko County, Nevada.

The species may be subdivided into four phases, for which names are available. The vast majority of populations have bright yellow flowers with pustulose bases and midveins. The pustulose condition may also be observed in Eriogonum chrysops (on pale greenish-yellow flowers) and in E. mancum (with cream-colored flowers). Populations with pale yellow flowers here assigned to E. crosbyae occur in the mountains near Mackay, Idaho, and cream-colored flowers are found near Challis and around Salmon, both well outside the known ranges of E. chrysops and E. mancum. Final resolution of the taxonomy of this group awaits further study.