Plants 2-7 dm, from bulbs; bulbs not clumped, tunicate, ovoid, 10-30 × 8-20 mm. Leaves: proximal blades 12-50 cm × 2-10 mm. Inflorescences racemose or paniculate with 1 or 2 basal branches, 10-50-flowered, terminal raceme pyramidal in anthesis, 2-20 × 2-5 cm, branches (if any) 1/10-1/3 length of entire inflorescence, diverging from main axis at 10°-60° when in fruit. Flowers: perianth hy-pogynous, campanulate, 5-10 mm diam.; tepals persistent in fruit, cream colored, 2-5 × 1-3 mm, outer often clawed, apex usually acute; gland 1, obovate, distal margins evident to obscure, irregular; filaments straight, usually equaling tepals, occasionally longer, thickened proximally; pedicel usually ascending in fruit, occasionally perpendicular to stem, 3-25 mm, bracts usually green, sometimes white, 5-25 mm. Capsules 8-20 × 4-7 mm. 2n = 22.

Zigadenus venenosus is a smaller, more slender plant than either Z. paniculatus or Z. fontanus. It can be distinguished from Z. micranthus by its ascending pedicels. It has a much broader distribution than either Z. micranthus or Z. fontanus, and does not occur on serpentine substrates.