Bulbs 2–10+, forming threadlike rhizomes, rhizomes 3–10 cm, terminated by bulbels and/or 1–2 basal bulbels that in turn may produce threadlike rhizomes, ± globose, 1–1.5 × 1–1.5 cm; outer coats enclosing single bulb, brown, membranous, lacking cellular reticulation or cells arranged in only 2–3 rows distal to roots, ± quadrate, without fibers; inner coats light yellow, turning reddish on drying, cells obscure, ± quadrate. Leaves persistent, withering from tip by anthesis, 1, basally sheathing, sheath not extending much above soil surface; blade solid, terete, 20–40 cm × 2–4 mm. Scape persistent, solitary, erect, solid, terete, 10–20+ cm × 1–5 mm. Umbel persistent, erect, compact, 12–30-flowered, globose, bulbils unknown; spathe bracts persistent, usually 3, 5–7-veined, lanceolate, ± equal, apex apiculate. Flowers campanulate, 12–14 mm; tepals spreading, unequal; outer tepals maroon, oblanceolate, margins irregularly shallow-toothed, apex acute to mucronate, reflexed-curled; inner tepals maroon distally, white proximally, ovate, withering in fruit, curled back at tip, margins entire, apex acute, reflexed; stamens included; anthers yellow; pollen yellow; ovary crested; processes 6, prominent, narrowly triangular, margins entire, apex emarginate; style linear, equaling stamens; stigma capitate, 3-lobed, lobes slender, recurved; pedicel 10–16 mm. Seed coat shining; cells minutely roughened. 2n = 14.
Phenology: Flowering Jun–Jul.
Habitat: Soil pockets on schist outcrops
Elevation: 2200–2400 m
Of conservation concern.
Allium shevockii is known only from the upper slopes of Spanish Needle Peak in the southern Sierra Nevada and from Horse Canyon, Tehachapi Mountains.