Bulbs 1-5, not clustered on stout primary rhizome, ovoid, 1-2 × 0.8-1.8 cm; outer coats enclosing 1 or more bulbs, brown, membranous, cellular-reticulate, cells quadrate, polygonal, or ± rectangular, ± transversely elongate, without fibers; inner coats white, reticulation absent or cells obscure, ± quadrate. Leaves usually deciduous with scape, withering from tip at anthesis, 1-2, basally sheathing, sheaths not extending much above soil surface; blade solid, flat or broadly channeled, ± falcate, 5-22 cm × 0.5-14 mm, margins entire. Scape usually forming abcission layer and deciduous with leaves after seeds mature, frequently breaking at this level after pressing, solitary, erect, solid, terete, 2-17 cm × 0.5-2 mm. Umbel persistent, erect, compact, 6-65-flowered, hemispheric, bulbils unknown; spathe bracts persistent, 2-3(-5), 5-8-veined, ovate, ± equal, apex abruptly acuminate to apiculate. Flowers campanulate, 4-12 mm; tepals erect, white or pink with dark purplish midveins, lanceolate to oblong-elliptic, ± equal, becoming papery in fruit, margins entire, apex obtuse to acute; stamens included; anthers yellow or purple; pollen yellow; ovary crested; processes 3, obscure to ± prominent, rounded, central, margins entire; style linear, equaling stamens or longer; stigma capitate, scarcely thickened, obscurely 3-lobed; pedicel 2-14(-20) mm. Seed coat dull; cells ± smooth.

Allium obtusum is known only from the Sierra Nevada.