# Allium of western North America
The **Allium** species of western North America are wild, bulb-forming perennials of meadows, sagebrush steppe, serpentine (unusual rock-derived soil where many species specialize) outcrops, and montane streambanks, quite distinct from the old-world crop onions, garlics, and chives covered elsewhere. Western North America hosts one of the two great centers of diversity of the genus *Allium*, the onions. Of the roughly 850 species in the genus worldwide, 84 are native to North America north of Mexico, and 60 of those occur in Washington, Oregon, and California; the California Floristic Province alone holds about 44 species, making it the center of distribution of the genus on the continent[1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641) • [2](https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf).
| Key fact | Detail |
|---|---|
| Genus size | ~850 species worldwide; 84 native to North America north of Mexico[1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641) |
| Western concentration | 60 of 84 North American species in WA, OR, and CA; California Floristic Province ~44 species[2](https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf) |
| Subgenus | 81 of 84 native species belong to subgenus *Amerallium* (x = 7)[1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641) • [3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086) |
| Californian section | All native Californian species sampled fall in section Lophioprason[4](https://pubmed.ncbi.nlm.nih.gov/18226928/) |
| Field characters | Scapose stem, 1–5 basal leaves, umbel, filaments fused into a ring, ovary with 0, 3, or 6 crests[5](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=9889) |
| Safety check | The onion smell is unique to *Allium* among southwestern amaryllis-family members; look-alikes such as crow poison may be harmful[6](https://sites.google.com/view/the-foraging-center/home/amaryllidaceae) |
| Conservation | 14 Oregon *Allium* taxa are listed as rare, threatened, endangered, or vulnerable[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf) |
## Taxonomy and regional clustering
*Allium* has been segregated from the old broad [Liliaceae](https://www.edgepedia.org/liliaceae) into its own family (now usually treated as [Amaryllidaceae](https://www.edgepedia.org/amaryllidaceae), subfamily Allioideae) by most recent authors, and the genus is currently divided into 15 subgenera and 72 sections[3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086) • [8](https://doi.org/10.5642/aliso.20062201.31). H. P. Traub recognized subgenus *Amerallium* in 1972 for the North American members with a base chromosome number of x = 7; all but three North American species (the rhizomatous *A. schoenoprasum*, *A. tricoccum*, and *A. victorialis*, with x = 8) fit there[3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086). Molecular work confirms that 81 of the 84 native species north of Mexico belong to this subgenus, which is monophyletic (descended from a single common ancestor) and sister to the rest of the genus together with subgenera *Nectaroscordum* and *Microscordum*[1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641).
**Molecular work has reshaped the classification.** A 2008 phylogeny using nuclear ribosomal ITS and ETS sequences from 39 native Californian species plus 154 GenBank sequences found the native North American species monophyletic with the exceptions of *A. tricoccum* and *A. schoenoprasum*[4](https://pubmed.ncbi.nlm.nih.gov/18226928/). A 2013 study of subgenus *Amerallium* sampled 74 species north of Mexico plus two Mexican endemics and found that only three of the eight informal morphological "alliances" of Ownbey's classification were strictly monophyletic; the authors proposed two sections for New World *Amerallium* and recommended keeping the informal alliances rather than formalizing subsections[1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641). Ownbey's alliances include the *A. acuminatum* alliance with 13 species and the *A. falcifolium* alliance with 27[9](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1300053).
All native Californian species in the 2008 analysis fell into the monophyletic section Lophioprason, though the endemic Californian species were not monophyletic because some range beyond the California Floristic Province[4](https://pubmed.ncbi.nlm.nih.gov/18226928/). A 2023 plastome phylogeny of 76 species confirmed 15 subgenera and 72 sections and found subgenera *Anguinum* and *Rhizirideum* monophyletic while several others, including *Allium*, *Cepa*, *Polyprason*, and *Melanocrommyum*, are highly polyphyletic; it also placed the North American *A. tricoccum* in the Eurasian clade of subgenus *Anguinum*[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC10070991/).
## How to recognize a western *Allium*
The genus is easy to place and hard to split. Jepson eFlora's diagnostic features are a leafless flowering stem (scape), 1–5 basal leaves, an umbel inflorescence sometimes partly replaced by bulblets, filaments fused into a ring, and an ovary bearing 0, 3, or 6 crests[5](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=9889). Within the genus, the shape and cell arrangement of the outer bulb coat is generally the most important identification character, and it usually must be determined with magnification[5](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=9889). Leaf anatomy adds deeper characters: leaf-blade shape in transection, presence or absence of palisade mesophyll, vascular bundle distribution, and orientation, and laticifer cell position are congruent with phylogenetic relationships and diagnostic within North American species[9](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1300053).
**Foragers should rely on smell.** The onion-like smell is unique to *Allium* among the southwestern members of the amaryllis family, and similar-looking plants such as crow poison (*Nothoscordum bivalve*) may be harmful[6](https://sites.google.com/view/the-foraging-center/home/amaryllidaceae).
## Representative species
Swamp onion (*Allium validum*) is a wet-meadow species of the [Sierra Nevada](https://www.edgepedia.org/sierra-nevada) and Cascades, extending to southwestern Idaho and eastern Oregon; its Rocky Mountain counterpart in similar habitats is *A. brevistylum*, from western Montana to northeastern Idaho[2](https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf). In Oregon it occurs at 500–2500 m in the [Blue Mountains](https://www.edgepedia.org/blue-mountains-pacific-northwest), High Cascades, and Calapooya Mountains, flowering June–September along streambanks[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf). Its bulbs are clustered on thick, iris-like rhizomes that produce new bulbs in succeeding years, an unusual habit in the genus[3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086) • [7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf). It has 3–6 grass-like leaves up to 80 cm long, winged scapes to 70 cm, and umbels of 15–30 bell-shaped flowers; [Sereno Watson](https://www.edgepedia.org/sereno-watson) described it in 1871 from a specimen collected by Henry Nicholas Bolander on Mt. Dana, Mono Pass, California[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf).
Tapertip onion (*Allium acuminatum*) may be the most common native onion in Oregon, flowering May–June in dry to seasonally moist meadows, prairies, sagebrush steppe, and open forest up to 2500 m[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf).
Prairie onion (*Allium textile*) has fibrous, reticulate bulb coats and 15–30 white, urn-shaped flowers with reddish midveins; its ovary bears six pronounced crests that are sometimes fused across the septa[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf). Aven Nelson and James Macbride described it in 1913 from their 1912 collections at [Shoshone Falls](https://www.edgepedia.org/shoshone-falls), Idaho, distinguishing it from *A. reticulatum*[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf). It is widespread in the [Rocky Mountains](https://www.edgepedia.org/rocky-mountains) and [Great Plains](https://www.edgepedia.org/great-plains) south to the Colorado–New Mexico border; in Oregon it is recorded from Harney, Lake, Malheur, Wallowa, and Wheeler counties, flowering May–June[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf).
Narrow-leaved onion (*Allium amplectens*) is a Californian species ranging to [British Columbia](https://www.edgepedia.org/british-columbia), growing on clays including serpentine in open or wooded places below 1800 m, flowering April–July[11](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12506). Its bulbs are 6–15 mm with outer coat cells transversely elongate in a wavy [herringbone pattern](https://www.edgepedia.org/herringbone-pattern), the umbels carry 10–50 flowers 5–9 mm long, the ovary has six obvious lateral crests, and chromosome counts are n = 7, 14, and 2n = 21[11](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12506). In Oregon it grows from sea level to 2500 m, flowers May–July, has 2–4 leaves 10–36 cm long, scapes to 50 cm, and umbels of star-shaped flowers that shatter individually after seed matures; it prefers clay soils and moist seeps including serpentine outcrops[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf). Its synonyms include *A. serratum* S. Watson and *A. occidentale* A. Gray[11](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12506). The evidence base does not cover *A. unifolium* in detail, so no species profile is given here.
## Habitats and distribution
Serpentine soils are a recurring theme in the Californian radiation: serpentine adaptation appears to have evolved multiple times within section Lophioprason, and the ancestor of the Californian center of diversity may not have been serpentine-adapted[4](https://pubmed.ncbi.nlm.nih.gov/18226928/). Elsewhere the species occupy montane streambanks (*A. validum*), dry steppe, and open forest (*A. acuminatum*), plains and rocky intermountain settings (*A. textile*), and clay seeps (*A. amplectens*)[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf) • [11](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12506).
**Phenology tracks snowmelt.** Most western United States *Allium* grow vegetatively in late winter or early spring, often under snowpack, flowering after snowmelt, and setting seed before the soils dry in late spring or early summer[2](https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf). The Columbia Basin assessment region alone holds 31 native species and two varieties[2](https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf), while Oregon's flora also includes old-world introductions such as *A. nigrum*, *A. triquetrum*, and *A. vineale*, and there is some question whether chives are native in the [Pacific Northwest](https://www.edgepedia.org/pacific-northwest)[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf).
## By the numbers
Estimates of the genus's size have grown as sampling has widened. Flora of North America recognizes 550–700 species worldwide with 96 in the North American flora[3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086); the 2013 *Amerallium* study put the genus at roughly 850 species[1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641); and a 2023 plastome study gives over 900[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC10070991/). For North America, the flora count of 96 includes non-natives, while 84 native species are recognized north of Mexico[3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086) • [1](https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641). Within the United States, Washington, Oregon, and California together hold 60 of the 84 species, and the California Floristic Province's roughly 44 species far exceed Texas's about 14[2](https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf). Elevation ranges span from sea level (*A. amplectens*) to 2500 m (several species)[7](https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf), and chromosome numbers center on x = 7, with *A. amplectens* counted at n = 7, 14, and 2n = 21[3](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086) • [11](https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12506).
## References
1. Molecular systematics of *Allium* subgenus *Amerallium* (Amaryllidaceae) in North America. American Journal of Botany. https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1200641
2. Report on *Allium* Columbia Basin Scientific Assessment Project. USDA Forest Service. https://www.fs.usda.gov/r6/icbemp/science/mcneal.pdf
3. *Allium* in Flora of North America (eFloras). http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086
4. A molecular phylogeny of the wild onions (*Allium*; Alliaceae) with a focus on the western North American center of diversity. Molecular Phylogenetics and Evolution, 2008. https://pubmed.ncbi.nlm.nih.gov/18226928/
5. Jepson eFlora: *Allium* (genus treatment). https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=9889
6. The Botany of Survival — Wild Onions. https://sites.google.com/view/the-foraging-center/home/amaryllidaceae
7. Call Me *Allium*: A Guide to Oregon's Native Onions. Native Plant Society of Oregon. https://www.npsoregon.org/documents/AlliumOccasionalPaper4.pdf
8. Phylogeny and New Intrageneric Classification of *Allium* (Alliaceae) Based on Nuclear Ribosomal DNA ITS Sequences. Aliso, 2006. https://doi.org/10.5642/aliso.20062201.31
9. Evolution of leaf blade anatomy in *Allium* (Amaryllidaceae) subgenus *Amerallium* with a focus on the North American species. American Journal of Botany, 2014. https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1300053
10. New insights into the phylogenetic relationships among wild onions (*Allium*, Amaryllidaceae), with special emphasis on the subgenera *Anguinum* and *Rhizirideum*, as revealed by plastomes, 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10070991/
11. Jepson eFlora: *Allium amplectens*. https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=12506
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*Topic: Encyclopedia › Life and health › Plants and algae › Seed plants › Monocots › Lilioid monocots and Asparagales › Allium (allium genus) › Western North American Allium species*
*Initially written Sep 17, 2026 · Reviewed: Sep 19, 2026 · Edited: Sep 19, 2026; Oct 11, 2026; Oct 15, 2026; Oct 25, 2026 · Last review: Sep 19, 2026*
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