Bulbs 1-2, not clustered on stout, primary rhizome, ovoid to subglobose, 1.5-2.5 × 1-2 cm; outer coats enclosing single bulb, gray-brown, membranous, lacking cellular reticulation or cells arranged in only 2-3 rows distal to roots, ± quadrate, without fibers; inner coats light brown or white, cells obscure, quadrate. Leaves persistent, withering from tip by anthesis, 1, basally sheathing, sheath not extending much above soil surface; blade solid, terete, 22-42 cm × 1-4 mm. Scape persistent, solitary, erect, solid, terete, 25-37 cm × 1-3 mm. Umbel persistent, erect, ± compact, 20-60-flowered, hemispheric, bulbils unknown; spathe bracts persistent, 3-4, 4-5-veined, ovate, ± equal, apex long-acuminate. Flowers campanulate, 7-8.5 mm; tepals erect, white, flushed with pink near dark pink midveins, ovate-elliptic, ± equal, becoming papery in fruit, margins erose, apex acute to apiculate, outer tepals with reflexed tips; stamens included; anthers yellow; pollen yellow; ovary crested; processes 6, prominent, ± triangular, margins erose; style linear, equaling stamens; stigma capitate, 3-lobed, lobes slender, recurved; pedicel 7-20 mm. Seed coat dull or shining; cells minutely roughened. 2n = 14.

Flowering late May--early Jul. Clay soils, including serpentine; of conservation concern; 300--600 m; Calif.

Allium jepsonii is disjunct in the foothills of the Sierra Nevada.