Garden Onion

Onion is commonly cultivated everywhere. There is a smaller onion-like plant with few flowered umbels which is cultivated in some places. The flower structure is similar to that of Allium cepa. This may represent a variety of Allium cepa.

Allium ascalonicum Linn., the shallot, is also cultivated rarely.

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.

Bulbs clustered, cylindrical to ovoid or almost rounded; coats papery, white to brownish or reddish. Scape up to 1 m tall, stout, fistular, usually inflated below the middle. Leaves cylindrical, fistular. Umbels spherical, densely flowered. Flowers stellate. Pedicels 3-4 times as long as the tepals. Tepals greenish-white, 4-5 mm long, oblong, obtuse. Filaments exserted, inner 2-toothed at the base.

Bulbs 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, 4–10, sheathing proximal 1/6–1/4 scape; blade fistulose, usually ± semicircular in cross section, 10–50 cm × 4–20 mm. Scape persistent, solitary, erect, fistulose, inflated below middle, 30–100 cm × 3–20 mm. Umbel 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 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 not known.

Bulb solitary or clustered, applanate-globose to cylindric-ovoid; tunic purple-red, brown-red, pale brown-red, or yellow to pale yellow, papery to thinly leathery, entire. Leaves shorter than scape, 0.5--2 cm wide, terete, fistulose. Scape developed or not, if developed then to 1 m, terete, conspicuously inflated below middle, fistulose, covered with leaf sheaths only at base. Spathe 2- or 3-valved, persistent. Umbel globose, densely many flowered or with bulblets and a few flowers. Pedicels equal, ca. 5 × as long as perianth, bracteolate. Perianth chalk white or white; segments with green or pale red midvein, oblong-ovate, 4--5 × ca. 2 mm. Filaments equal, slightly longer than perianth segments, connate at base for ca. 1/5 their length, adnate to perianth segments for 1/2 of connate part; outer ones subulate; inner ones broadened at base, 1-toothed on each side. Ovary subglobose, with concave nectaries covered by hoodlike projections at base. Style slightly exserted. Fl. and fr. May--Jul. 2 n = 16*, 32.

Ark., Calif., Kans., La., Mont., Oreg., Tex., Wash.; cultivated in Europe, Asia.

Fl.Per.: Summer months.

Flowering Jun--Aug.

Disturbed sites adjacent to areas where cultivated; 0--500m.

Cultivated as a vegetable. Throughout China [widely cultivated elsewhere].