Allium cepa
Garden onion
(c) petitcrabe, some rights reserved (CC BY) · licence
Family: Alliaceae · Type: Herb · Not Native
Allium cepa (Garden onion) is a non-native California herb in the Alliaceae family.
Garden onion is a naturalized perennial found in disturbed agricultural and transport areas at elevations below 500 meters. Flowering from July to August, this plant produces white to pink or light green flowers in clusters of 150 to 500 blooms, forming star- to bell-shaped flower heads. Growing with hollow stems 30 to 100 centimeters tall that are inflated below the middle, it develops a depressed-spherical bulb 5 to 8 centimeters wide with white, yellow, brown, or red outer layers. Its leaves are 4 to 10 in number, 10 to 50 centimeters long and 4 to 20 millimeters wide, sheathing the lower portion of the stem and generally semicircular in cross-section. The bulb contains multiple layers and is the familiar culinary onion used in cooking worldwide.
Identification and appearance
Key characters: Geographically isolated - cultivated escape with distinctive morphology
Habitat and range
Habitat: The onion of commerce, found along roadsides, disturbed places near where plants are grown commercially or along routes of transport
Elevation: < 500 m
Outside California: world-wide
Bloom period
Allium cepa blooms Jul-Aug.
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 cepa native to California?
No. Allium cepa is not native to California (recorded as not native).
When does Allium cepa bloom?
Allium cepa blooms Jul-Aug.
What plant family does Allium cepa belong to?
Allium cepa is in the Alliaceae family, genus Allium.
What habitat does Allium cepa grow in?
Allium cepa grows in The onion of commerce, found along roadsides, disturbed places near where plants are grown commercially or along routes of transport.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.