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Montana Field Guide

Montana Field Guides

Tapertip Onion - Allium acuminatum

Species of Concern
Native Species

Global Rank: G5
State Rank: S2S3
(see State Rank Reason below)
State Threat Score: High - Medium
CCVI: Moderately Vulnerable

Agency Status
USFS: Sensitive - Known in Forests (BRT, KOOT, LOLO)
Sensitive - Suspected in Forests (BD)



External Links

State Rank Reason (see State Rank above)
Rare in Montana, where it is known from several widely scattered sites in the western half of the state. Trend data are lacking. Threats to populations do not appear to be significant at this time, though invasive weeds may eventually pose problems at some sites.
General Description
Bulbs sometimes clustered, globose; outer coat dingy white, membranous, honeycombed. Scapes terete, 20–35 cm. Leaves 2 to 3, subterete to channeled, 0.5–2 mm wide, withering. Umbel hemispheric with 10 to 30 flowers; pedicels 5–25 mm long; bracts 2, lanceolate to ovate, acuminate. Flowers pink to magenta; outer tepals 7–14 mm long; inner tepals smaller; ovary obscurely crested; stamens included. Seed surface minutely roughened (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Flowering May-June.

Diagnostic Characteristics
Allium acuminatum can be distinguished from most other species by having the combination of rose-colored outer tepals that are longer than the inner tepals, and more than 2 concave leaves. The more common A. brevistylum also has rose-colored tepals, but its leaves are usually more than 4 mm wide.

Species Range
Montana Range Range Descriptions


Range Comments
BC, MT south to CA, AZ and NM. Known from Ravalli and Sanders counties (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 43

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Dry, open forests and grasslands in the montane zone.
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus bifarius, Bombus centralis, Bombus flavifrons, Bombus huntii, Bombus melanopygus, Bombus sylvicola, Bombus occidentalis, and Bombus bohemicus (Macior 1974, Thorp et al. 1983, Colla and Dumesh 2010, Koch et al. 2012, Miller-Struttmann and Galen 2014, Williams et al. 2014).

Threats or Limiting Factors
Reported threats to Montana’s populations of Tapertip Onion include severe potential threats to roadside populations if a road widening project takes place without mitigation. More than half of the state populations are located along a highway where proposed road construction may potentially damage or destroy plants, populations and habitat. Information on the status of this project, or knowledge of the population's existing condition is needed. Noxious weeds are reported to threaten other populations, where negative impacts due to chemical herbicide application are also a concern. Another potential threat due to development of recreation areas was reported, but information about the scope, severity, and timing is needed to assess its relative risk (MTNHP Threat Assessment 2021).

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Macior, L.M. 1974. Pollination ecology of the Front Range of the Colorado Rocky Mountains. Melanderia 15: 1-59.
    • Miller-Struttmann, N.E. and C. Galen. 2014. High-altitude multi-taskers: bumble bee food plant use broadens along an altitudinal productivity gradient. Oecologia 176:1033-1045.
    • Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
    • Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ: Princeton University Press. 208 p.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Culver, D.R. 1994. Floristic analysis of the Centennial Region, Montana. M.Sc. Thesis. Montana State University, Bozeman. 199 pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
    • Quire, R.L. 2013. The sagebrush steppe of Montana and southeastern Idaho shows evidence of high native plant diversity, stability, and resistance to the detrimental effects of nonnative plant species. M.Sc. Thesis. Bozeman, MT: Montana State University. 124 p.
    • Simanonok, M. 2018. Plant-pollinator network assembly after wildfire. Ph.D. Dissertation. Bozeman, MT: Montana State University. 123 p.
  • Web Search Engines for Articles on "Tapertip Onion"
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Citation for data on this website:
Tapertip Onion — Allium acuminatum.  Montana Field Guide.  .  Retrieved on , from