57. Allium rhizomatum Wooton & Standley, Contr. U.S. Natl. Herb. 16: 114. 1913.
Bulbs solitary, not basally clustered, replaced annually by new bulbs borne terminally on rhizome; rhizomes 1–3, conspicuous, slender, 2–3 cm, scaly; parent bulbs persisting, often not collected, oblique-ovoid, 1–2.5 × 1 cm; outer coats enclosing parent bulbs, grayish, lacking cellular reticulation, membranous, without fibers; inner coats white or hyaline, cells obscure, ± quadrate. Leaves persistent, green at anthesis, 2–3, basally sheathing, sheaths not extending much above soil surface; blade solid, flat, not falcate, 20–35 cm × 2–3 mm, margins entire. Scape solitary, erect, solid, terete, 20–30 cm × 1–3 mm. Umbel persistent, erect, loose, 5–15(–22)-flowered, globose to hemispheric, bulbils unknown; spathe bracts persistent, 2, 3-veined, ovate to lance-ovate, ± equal, apex acute. Flowers stellate, 6–9 mm; tepals erect, pink with purplish or pinkish midveins, oblong to lanceolate, slightly carinate basally, ± equal, becoming papery in fruit, margins entire, apex acute to acuminate; stamens included; anthers yellow or pink; pollen yellow or white; ovary crestless, 3-grooved with thickened ridge on either side of groove; style linear, shorter than stamens; stigma capitate, scarcely thickened, unlobed; pedicel 10–20(–50) mm. Seed coat shining; cells smooth. 2n = 28.
Flowering Jul--Sep. Dry, usually grassy areas; 1200--2200 m; Ariz., N.Mex., Tex.; Mexico.
Allium rhizomatum has often been included within the Mexican species A. glandulosum. This reduction is unwarranted. The perianth of A. rhizomatum is pale, with the color mainly confined to the midribs. Additionally, the species can be distinguished by its 3-lobed, apically 3-grooved ovary and lack of sepal glands. Allium glandulosum has a red perianth, an apically rounded ovary, and sepal glands. The nectar produced from these glands does not show in herbarium specimens.