Allium rhizomatum |
Allium cepa |
|
---|---|---|
spreading wild onion |
cultivated onion, garden onion |
|
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. |
1–3, not rhizomatous, mostly depressed-globose, varying in size from cultivar to cultivar, 5–8 × 3–10 cm; outer coats enclosing 1 or more bulbs, yellowish brown, red, or white, membranous, without reticulation; inner coats white to pink, cells obscure to 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. |
persistent, 4–10, sheathing proximal 1/6–1/4 scape; blade fistulose, usually ± semicircular in cross section, 10–50 cm × 4–20 mm. |
Scape | solitary, erect, solid, terete, 20–30 cm × 1–3 mm. |
persistent, solitary, erect, fistulose, inflated below middle, 30–100 cm × 3–20 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. |
persistent, erect, compact, to 500-flowered, globose, bulbils occasionally found; spathe bracts caducous, 2–3, 3–4-veined, ovate, ± equal, apex acute to acuminate. |
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. |
stellate to campanulate to urceolate, 3–7 mm; tepals erect to ± spreading, white to pink with greenish midveins, withering in fruit, margins entire, apex obtuse or acute, outer ovate, inner oblong; stamens exserted; anthers white; pollen white; ovary crestless; style linear, ± equaling stamens; stigma capitate, unlobed; pedicel 10–50 mm. |
Seed | coat shining; cells smooth. |
coat not known. |
2n | = 28. |
|
Allium rhizomatum |
Allium cepa |
|
Phenology | Flowering Jul–Sep. | Flowering Jun–Aug. |
Habitat | Dry, usually grassy areas | Disturbed sites adjacent to areas where cultivated |
Elevation | 1200–2200 m (3900–7200 ft) | 0–500 m (0–1600 ft) |
Distribution |
AZ; NM; TX; Mexico
|
AR; CA; KS; LA; MT; OR; TX; WA; cultivated in Europe; Asia
|
Discussion | 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. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
The onion of commerce, Allium cepa is widely cultivated as a biennial in North America, Europe, and Asia. It is unknown in the wild and is probably derived from A. oschanini of central Asia. The cultivated form is often polyploid (2n = 16, 32, 54) and possibly of hybrid origin. It exists in numerous cultivars, a few of which form large bulbils in the umbel. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 26. | FNA vol. 26, p. 244. |
Parent taxa | Liliaceae > Allium | Liliaceae > Allium |
Sibling taxa | ||
Name authority | Wooton & Standley: Contr. U.S. Natl. Herb. 16: 114. (1913) | Linnaeus: Sp. Pl. 1: 301. (1753) |
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