Allium unifolium
One leaf onion
(c) Trevor Van Loon, some rights reserved (CC BY), uploaded by Trevor Van Loon · licence
Family: Alliaceae · Type: Herb · Native
Allium unifolium (One leaf onion) is a native California herb in the Alliaceae family, recognized by distinctive rhizome system with terminal bulbs.
One leaf onion is a California native perennial found in northwestern and central western California in moist clay or serpentine areas, especially grassy streambanks at elevations below 1,100 meters. Flowering from May to June, this plant produces delicate pink or white flowers in clusters of 15 to 35 blooms with pedicels 15 to 40 millimeters long. Growing with slender stems 30 to 80 centimeters tall, it develops from a small ovoid bulb with 1 to 3 obvious rhizomes that produce new bulbs at their tips. Its leaves are 2 to 3 in number, shorter than the stem, widely channeled or nearly flat, and keeled. The bulb has a pale brown outer coat with subtle rectangular cell patterns.
Identification and appearance
Key characters: 38 sympatric species; distinctive rhizome system with terminal bulbs is diagnostic
Habitat and range
Habitat: Uncommon. Moist clay or serpentine, especially grassy streambanks
Elevation: < 1100 m
California counties: Lake, Monterey, San Francisco, Humboldt, Santa Cruz, Mendocino, Santa Clara, Napa, San Luis Obispo, Stanislaus, San Mateo, Contra Costa, Alameda, Riverside, Del Norte, San Benito, Marin, Sonoma, San Diego
Outside California: Oregon
Bloom period
Allium unifolium blooms May-Jun.
How to tell it apart
vs Triteleia: Allium smells like onion when crushed; triplet lily has no smell.; vs Agapanthus: Allium smells like onion; lily-of-the-Nile has no smell and much larger flowers.; vs Dipterostemon: Allium smells like onion when crushed; ookow has no onion smell.; vs Nothoscordum: Allium smells like onion when crushed; false garlic has no smell.; vs Tulbaghia: Allium has flowers in tight umbels; society garlic has flowers in loose open clusters.
Frequently asked questions
Is Allium unifolium native to California?
Yes. Allium unifolium is native to California (recorded as native).
When does Allium unifolium bloom?
Allium unifolium blooms May-Jun.
Where in California does Allium unifolium grow?
Allium unifolium occurs in Lake, Monterey, San Francisco, Humboldt, Santa Cruz, Mendocino, Santa Clara, Napa and other counties, at elevations of < 1100 m.
What plant family does Allium unifolium belong to?
Allium unifolium is in the Alliaceae family, genus Allium.
What habitat does Allium unifolium grow in?
Allium unifolium grows in Uncommon. Moist clay or serpentine, especially grassy streambanks.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.