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Montana Field Guide

Montana Field Guides

Small Onion - Allium parvum

Species of Concern

Global Rank: G5
State Rank: S3
* (see State Rank Reason below)

Agency Status
USFWS:
USFS: SENSITIVE
BLM:
MNPS Threat Rank:
C-value:

External Links






State Rank Reason (see State Rank above)
Known from southwest Montana, primarily on the Bitterroot National Forest. Many of the the documented occurrences have large numbers of individuals and cover extensive areas. However, many of the sites are also infested with spotted knapweed and/or cheatgrass and continued increases in the density and spread of both invasive weeds are likely, further degrading the habitat occupied by Allium parvum.
  • Details on Status Ranking and Review
    Small Onion (Allium parvum) Conservation Status Review
    Review Date = 06/11/2012
    View State Conservation Rank Criteria
    Population Size

    Score1 - Moderate: Generally 10,000-100,000 individuals.

    Range Extent

    Score2 - Regional or State Endemic or Small Montana Range: Generally restricted to an area <100,000 sq. miles (equivalent to 2/3 the size of Montana or less) or Montana contributes 50% or more of the species’ range or populations OR limited to 2-3 Sub-basins in Montana.

    Area of Occupancy

    Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).

    Environmental Specificity

    Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).

    Trends

    Score0-1 - Stable to Minor Declines:

    CommentTrends are undocumented, though populations are likely stable or experiencing only minor declines.

    Threats

    Score1-2 - Medium to High.

    CommentInvasive species and associated control efforts are the primary threats.

    Intrinsic Vulnerability

    Score0-1 - Low to Moderate Vulnerability.

    Raw Conservation Status Score

    Score 6 to 9 total points scored out of a possible 19.

 
General Description
Bulbs usually ovoid; outer coat membranous mostly without reticulations. Scapes flattened, 3–6 cm. Leaves 2, flat, falcate, 1–4 mm wide, persistent. Umbel congested-hemispheric with 5 to 30 flowers; pedicels 5–10 mm long; bracts 2, ovate, acute to acuminate. Flowers: tepals white with a purple midvein; 8–12 mm long; ovary with 3 crests adjacent to the style; stamens included. Seed surface smooth (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Phenology
Flowering in late May-June.

Diagnostic Characteristics
The flattened stem and fine-textured bulb coats separate this species from the similar A. simillimum, A. textile and A. brandegeei.

Species Range
Present
 


Range Comments
Eastern OR to CA, east to ID, NV, and southwest MT. Peripheral.

Summary of Observations Submitted for Montana
Number of Observations: 176

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

Recency

 

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



Habitat
Dry, open forests, woodlands, or grasslands on warm slopes in the montane zone.

References
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Citation for data on this website:
Small Onion — Allium parvum.  Montana Field Guide.  .  Retrieved on , from