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Allium anceps Kellogg

Twinleaf onion; Kellogg's onion

Liliaceae (Lily family)

General Description: Perennial forbs with broadly egg-shaped underground bulbs having a thick, yellowish, cellular-patterned coat. Bulbs give rise to a flattened, minutely scabrous-margined stem about 10-15 cm tall; each with a pair of sickle-shaped, scabrous-margined leaves 4-6 mm wide and up to twice as long as the scape. The leaves fall off the plant at maturity. Stems are terminated by an umbel containing 15-25 pinkish-colored flowers that have a diffuse green midrib. The slender, lance-linear-shaped tepals are 6-10 mm long and attached to the umbel by pedicels roughly three times as long as the tepals.

Illustration.

Field Identification Tips: The flattened stems; pair of relatively narrow, more-or-less sickle-shaped leaves; slender, lance-linear-shaped tepals; and stamens equaling or shorter than the tepals provide a combination of field characteristics to help distinguish Allium anceps.

Phenology: Flowering begins in the spring, sometimes by early April, and continues into June.

Similar Species: About ten other onion species overlap the range of Allium anceps in Idaho. It is most likely to be confused with several that also possess a pair of sickle-shaped leaves, including A. lemmonii (Lemmon's onion), A. tolmiei (Tolmie's onion), and A. parvum (small onion). Allium anceps has slender tepals mostly more than 4 times as long as wide, compared to tepals mostly less than 4 times as long as wide for the other three species. One or more differences in bulb coat, leaf length and width, tepal and midrib color, and stamen length characters can also be used to separate A. anceps from these similar species.

Photo © Robert K. Moseley CLICK PHOTO FOR A LARGER IMAGE

Habitat: Heavy soils of volcanic origin in or around seasonally wet playas, swales, and other low places, or thin, rocky soil in the sagebrush zone. Sites are usually flat to gently sloping, and sparsely vegetated.

Global Distribution: Widespread in Nevada, extending into northeastern California, southeastern Oregon, and southern Idaho.

Idaho Distribution: Most known Idaho populations are in Twin Falls County. One occurrence is also known from Jerome County north of the Snake River. Populations in Owyhee and Cassia counties should also be expected.

References:

DeBolt, A. 1989. An illustrated guide to the sensitive plants of Burley District, Bureau of Land Management. Technical Bulletin 89-3. Bureau of Land Management, Boise, ID.

McClain, P. 1998. An illustrated guide to the special status plants of the Shoshone Resource Area (Upper Snake River District). Technical Bulletin 98-7. Bureau of Land Management, Boise, ID.