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Montana Field Guide

Montana Field Guides

Gray's Milkvetch - Astragalus grayi

Species of Concern
Native Species

Global Rank: G4?
State Rank: S2S3
(see State Rank Reason below)

Agency Status
MNPS Threat Rank:

External Links

State Rank Reason (see State Rank above)
Rare in the state. Locally restricted to Carbon and Big Horn counties. Population levels, trends and threats to the species are poorly documented. Additional information is needed for the species within Montana.
  • Details on Status Ranking and Review
    Gray's Milkvetch (Astragalus grayi) Conservation Status Review
    Review Date = 05/14/2013
    View State Conservation Rank Criteria
    Population Size

    Score2 - Small: Generally 2,000-10,000 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.

    CommentRegional endemic of Wyoming, extending into south-central Montana. Documented from 3 sub-basins in Montana.

    Area of Occupancy

    Score2 - Low: Generally occurring in 4-10 Subwatersheds (6th Code HUC’s).

    Environmental Specificity

    Score1-2 - Moderate to High.


    ScoreNA - Rank factor not assessed.


    Score1 - Medium: 11-30% of the populations are being negatively impacted or are likely to be impacted by one or more activities or agents, which are expected to result in decreased populations and/or habitat quality and/or quantity.

    CommentSeveral populations are near or adjacent to roads and may be impacted by associated activities.

    Intrinsic Vulnerability

    Score0-1 - Low to Moderate Vulnerability.

    Raw Conservation Status Score

    Score 8 to 10 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Gray's Milkvetch is an herbaceous perennial with numerous, simple or branched stems, 20-35 cm long and arising together from a branched rootcrown just below the ground. Alternate, pinnately compound leaves are 4-10 cm long with 3-11 wire-like leaflets. Leaves are rather stiff and often held erect or ascending. Foliage is thinly covered with long hairs. Unbranched inflorescences, 2-7 cm long, arise from the axils of upper leaves and have 9-27 somewhat congested, ascending flowers. Cream-colored, pea-like flowers have a partly reflexed upper petal that is 15-23 mm long and a calyx that is 6-10 mm long and thinly to densely covered with long white or black hairs. Oblong pods are green and fleshy, glabrous, round in cross section, and 9-18 mm long.

Flowering and fruiting in June.

Diagnostic Characteristics
The combination of narrow, wire-like leaflets, no wider than the axis of the leaf, and erect stems and fruits is diagnostic. Astragalus pectinatus has similar foliage, but the pods are deflexed, and the stems often lie on the ground.

Species Range
Montana Range


Range Comments
South-central MT and western WY. Regional endemic.

Observations in Montana Natural Heritage Program Database
Number of Observations: 23

(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)

Open soil in sagebrush steppe in the valley zone.

Ecological Systems Associated with this Species

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.
    • Lesica, P. and P.L. Achuff. 1992. Distribution of vascular plant species of special concern and limited distribution in the Pryor Mountain desert, Carbon County, Montana. Unpublished report to the Bureau of Land Management. Montana Natural Heritage Program, Helena, MT. 105 pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
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Citation for data on this website:
Gray's Milkvetch — Astragalus grayi.  Montana Field Guide.  .  Retrieved on , from