Allium bisceptrum var. bisceptrum

Allium bisceptrum Wats. var. bisceptrum 

twin-crest onion 

Liliaceae (Lily Family) 

Status: State Review Group 1 

Rank: G4G5T3T5S1 

General Description: Adapted from Hitchcock et al. (1969): This bulbbearing 

perennial forb grows from 4 to 16 in. (10 to 40 cm) tall and commonly 

produces a cluster of short-stalked ovoid basal bulblets, with inner 

bulb coats that are either whitish or pinkish, and outer coats that are 

brownish and cellular-reticulate. There are 2 or more leaves per bulb, 

which are channeled, concave-convex in cross section, 1/32 to ½ in. (1 to 

13 mm) broad, usually shorter than the scape, green at anthesis, and 

persistent at maturity. The scape is 4 to 16 in. (10 to 40 cm) tall and 

more or less circular in cross section. Often there are 2 or more scapes 

arising successively from the more vigorous bulbs. There are 2 distinct 

bracts per plant, which are ovate to lanceolate, acuminate, and 3- to 5nerved. 

The umbel is usually many flowered, with pedicels 2 to 3 times 

the perianth length, which do not become strongly flexuous. The outer 

pedicels deflex in fruit. The lilac or pale pink to white perianth segments 

are ¼ in. (7 to 10 mm) long and broadly to narrowly lanceolate, acuminate, 

or entire. The perianth is thin, becoming papery as fruit matures. 

The ovary has 6 flattened, papillose-denticulate crests with a capitate 

stigma. The seeds are black, and the alveoli are minutely roughened or 

have a minute, pimplelike elevated area in the center. 

Identification Tips: Allium bisceptrum var. bisceptrum closely resembles 

A. campanulatum; however, these two species can be distinguished by 

their appearance at anthesis and perianth in fruit. The leaves of A. 

bisceptrum are usually green at anthesis, the perianth segments are 

usually papery in the fruit, and the tips of the perianth are rarely either 

strongly involute or with a pronounced keel. The leaves of A. 

campanulatum are commonly withering by anthesis, the perianth segments 

are rigid in the fruit, and the tips of the perianth are strongly involute 

and usually with a pronounced keel. 

Phenology: The variety flowers from May to July. 

Range: This species has been seen on the east face of the Cascade 

Mountains and the Sierra Nevada from Klamath County, Oregon, to Inyo 

County, California, and down the Pit River to Shasta County, California. It 

has also been found in the eastern desert ranges across Nevada, Idaho, 

and Utah. A. bisceptrum is disjunct from central Idaho to northern Idaho 

and in eastern Washington. This taxon has also been seen in Franklin 

County, Washington. 

Known distribution of Allium 

bisceptrum v. bisceptrum 

in Washington 

Current (1980+) 

Historic (older than 1980) 

Allium bisceptrum var. bisceptrum 


©1969 Reprinted by permission 

of the University of Washington Press. 

Illustration by Jeanne R. Janish



Photo by Gary A. Monroe 



2003 Produced as part of a cooperative project between the Washington Department of Natural Resources, Washington 

Natural Heritage Program and the U.S.D.I. Bureau of Land Management. Persons needing this information in an 

alternative format, call (360) 902-1600 or TTY (360) 902-1125. 



Habitat: This taxon occurs in meadows and aspen groves and grows 

less frequently on open slopes. In Washington, this taxon has been 

found at an elevation of 850 ft (259 m). This generally high-elevation 

plant is found in other regions from 6562 to 9514 ft (2000 to 2900 m). 

Associated species in Washington include sagebrush (Artemisia sp.), 

clematis (Clematis sp.), rose (Rosa sp.), brome (Bromus sp.), 

chokecherry (Prunus virginiana), poison ivy, oak, and sumac (Toxicodendron 

spp.), thistle (Cirsium sp.), and sedge (Carex sp). 

Ecology: This plant prefers the damp shade of aspen groves or open 

meadows in the pinyon-juniper and subalpine zones. In Washington, the 

one known population was found on bench above a river in a highly 

disturbed shrub steppe. 

State Status Comments: Only one small population has been found in 

the state. The Washington Natural Heritage Program needs more 

information before assigning an accurate status. 

Inventory Needs: Franklin County should be systematically surveyed 

for additional occurrences and updated information about these populations 

should be collected. The one documented occurrence should be 

re-visited and its identification should be confirmed. 

Threats and Management Concerns: Serious threats include competition 

from non-natives, trampling, and grazing. 

References: 

Anderson, M.K. Aspen Onion. Plant Guide. Natural Resources 

Conservation Guide. United States Department of Agriculture. 

August 14, 2003. 

Hitchcock, C.L., A. Cronquist, M. Ownbey, J.W. Thompson. 1969. 

Vascular Plants of the Pacific Northwest Part 1: Vascular Cryptogams, 

Gymnosperms, and Monocotyledons. University of Washington 

Press, Seattle, WA. 914 pp. 

2003 Produced as part of a cooperative project between the Washington Department of Natural Resources, Washington 

Natural Heritage Program and the U.S.D.I. Bureau of Land Management. Persons needing this information in an 

alternative format, call (360) 902-1600 or TTY (360) 902-1125.

Allium bisceptrum var. bisceptrum

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