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Allium unifolium

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About One Leaf Onion (Allium unifolium) Allium unifolium, the one-leaf onion or American garlic, is a North American species of wild onion. It is native to the coastal mountain ranges of California, Oregon, and Baja California. It grows on clay soils including serpentine, at elevations up to 1100 m. Allium unifolium, despite its name, usually has 2-3 flat leaves up to 50 cm long. Bulbs, though, are usually solitary, egg-shaped, up to 2 cm long, often formed at the end of rhizomes spreading out from the parent plant. Scapes are round in cross-section, up to 80 cm tall. Flowers are up to 15 mm across; tepals usually pink but occasionally white; anthers yellow or purple.

Plant Description
Plant Type
Perennial herb

Max. Height
1 - 2.6 ft (0.3 - 0.8 m)

Max. Width
1 in (3cm)

Upright Columnar


Growth Rate

Summer Deciduous

This plant produces one to four slender, strap-like leaves, up to 50 cm long, that accompany the inflorescence. It is a monocot with parallel venation.

Flower Color
Lavender, Pink, Yellow, White, Purple

Flowering Season

Native Status

Natural Setting
Site Type
Pockets of grassland within forest or chaparral, or grassy streambanks with moist clay soils, in the Coast Ranges and foothills

Full Shade, Part Shade

Elevation ?
22' - 4155'

Annual Precip. ?
10.5" - 77.7"

Summer Precip. ?
0.22" - 1.62"

Coldest Month ?
40.7° F - 51.3° F

Hottest Month ?
58.8° F - 79.0° F

Humidity ?
0.04 vpd - 25.23 vpd

Soil Description
Prefers heavy soils but tolerates a variety of garden soils. Tolerates serpentine soils

Soil Texture
Clay Loam, Loam, Loamy Sand, Sandy Clay, Sandy Clay Loam, Sandy Loam, Silt Clay Loam, Silt Loam, Silty Clay

Soil PH
7.0 - 9.0


Cold Tolerance(° F)
Tolerates cold to 10° F

Sunset Zones ?
4, 5, 6, 7*, 8, 9*, 14*, 15*, 16*, 17*, 18, 19*, 20*, 21*, 22*, 23*, 24*

Companion Plants
Native grasses, Miner's Lettuce, Dudleya spp,

Landscaping Information
Ease of Care
Very Easy

Water Requirement ?
Extremely Low
Very Low
Moderate - High

Seldom Used

Max. Summer Water ?
No Summer Water
No Summer Water
Keep moist

Organic with Rocks

Common uses
Butterfly Gardens, Deer Resistant, Bee Gardens

Nursery Availability
Commonly Available

Other Names
Common Names
Oneleaf Onion

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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