Subshrubs or shrubs, erect to spreading, not scapose, 0.2-1.5 × (0.6-)1-13(-16) dm, white- to tannish-tomentose, floccose, or glabrous. Stems spreading to erect, typically without persistent leaf bases, up to 1/ 2 height of plant; caudex stems absent or spreading; aerial flowering stems erect to spreading, slender, solid, not fistulose, 0.05-1.5 dm, lanate, tomentose, floccose, subglabrous, or glabrous. Leaves cauline, 1 per node or fasciculate; petiole 0.1-0.5 cm, tomentose to floccose or glabrous; blade usually elliptic, sometimes linear to obovate, 0.3-3.5 × (0.07-)0.1-1.2 cm, tomentose abaxially, less so or glabrous adaxially, margins occasionally revolute. Inflorescences cymose, compact, often flat-topped, 0.5-6(-12) × 1-10(-13) cm; branches dichotomous, whitish-lanate to brownish- or reddish-tomentose to floccose or glabrate, infrequently green or gray and subglabrous or glabrous; bracts 3, scalelike, linear to triangular, 1-5 mm. Peduncles absent or mostly erect, slender, 0.3-1.5 cm, tomentose to floccose. Involucres 1 per node, turbinate, (1.5-)2-3.5(-4) × 1.3-2.5(-3) mm, tomentose, floccose, subglabrous, or glabrous; teeth 5, erect, (0.3-)0.5-1(-1.7) mm. Flowers 1.5-3(-4) mm; perianth yellow or white to pink, orange, rose, red, or occasionally cream, glabrous; tepals connate proximal 1/ 2/ 5, essentially monomorphic, oblong to obovate; stamens usually exserted, 2.5-4 mm; filaments sparsely to densely puberulent proximally. Achenes brown, 1.5-3 mm, glabrous.
Eriogonum microthecum is used as browse by deer and to a lesser degree by cattle and sheep. Some forms are now in cultivation. The species is reportedly used by the Piute of Nevada in the treatment of tuberculosis, lameness, rheumatism, and bladder trouble (P. Train et al. 1941). S. A. Weber and P. D. Seaman (1985) stated that A. F. Whiting found the plants being used as a tea by the Havasupai in northern Arizona. Members of E. microthecum are food plants for subspecies of the rare pallid blue butterfly (Euphilotes pallescens). Also found on this species is the cythera metalmark (Apodemia mormo cythera). Some authors have referred E. effusum to this species, even though the ranges of the two species do not overlap and intermediates are unknown.