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Montana Field Guides

Summer Milkvetch - Astragalus hyalinus

Native Species

Global Rank: G4
State Rank: S4
(see State Rank Reason below)

Agency Status
MNPS Threat Rank:

External Links

State Rank Reason (see State Rank above)
S4 non-SOC: Astragalus hyalinus occurs within three counties of Montana; however, populations appear to be frequently present and many populations large.
  • Details on Status Ranking and Review
    Summer Milkvetch (Astragalus hyalinus) Conservation Status Review
    Review Date = 09/23/2016
    View State Conservation Rank Criteria
    Population Size

    ScoreF - 10,000 - 100,000 individuals

    Range Extent

    ScoreE - 5,000-20,000 sq km (~2,000-8,000 sq mi)

    Area of Occupancy

    ScoreE - 26-125 4-km2 grid cells

    Number of Populations

    ScoreD - 81 - 300

    Number of Occurrences or Percent Area with Good Viability / Ecological Integrity

    ScoreE - Many (41-125) occurrences with excellent or good viability or ecological integrity

    Environmental Specificity

    ScoreC - Moderate. Generalist or community with some key requirements scarce

    Long-term Trend

    ScoreU - Unknown


    ScoreU - Unknown


    ScoreU - Unknown

    CommentThreats: Unknown/undetermined.

    Intrinsic Vulnerability

    ScoreU - Unknown

General Description
Plants: Low tufted perennial, in time forming rounded cushions 10-40 cm across with a thick taproot; caudex woody, closely branched, covered with tenacious stipules and petioles; stems up to 2 cm in length or merely crowns with leaves in rosettes and overlapping stipules; herbage strigose and villous all over, silvery from ax-shaped trichomes up to 20 mm in length (McGregor et al. 1986).

Leaves: Leaves trifoliate, 5-40 mm in length (McGregor et al. 1986); leaflets oblanceolate, 3-10 mm in length, acute; stipules 2–7 mm in length, hyaline, united behind the petiole (Lesica 2012), the sheath ciliate and creased crosswise (McGregor et al. 1986).

Inflorescence: Peduncles up to 3.5 mm in length or not apparent, concealed by stipules; pedicels unapparent (McGregor et al. 1986); inflorescence having 1 or 2 flowers, shorter than leaf petioles (Lesica 2012).

(Lesica's contribution adapted from Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.)

June-July (McGregor et al. 1986).

Diagnostic Characteristics
Petals are white during the pollination period, wilt to yellowish, and remain on the plant another 2-3 weeks. This explains labels with flower color recorded as yellow (McGregor et al. 1986).

Species Range

Range Comments
Southeastern MT, sw SD, s to ne KS, ne CO, e 1/2 WY (McGregor et al. 1986). Endemic to Carbon and Big Horn counties and adjacent WY (Lesica's contribution from Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.)

Observations in Montana Natural Heritage Program Database
Number of Observations: 91

(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)

Sandy or stony soil of sparsely vegetated sagebrush steppe, pine woodlands; plains, valleys (Lesica 2012), rocky prairie hills (McGregor et al. 1986).

(Lesica's contribution adapted from Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.)

Reproductive Characteristics
Flowers: Calyx white-sericeous, the sepals 3-4 in length (Lesica 2012). Petals whitish when fresh, becoming yellowish with age, with long, soft hairs dorsally; keel- and wing- tips often tinged with purple, the keels 10-13 mm and the wings 10-17 mm in length; banner shaped like a narrow fiddle, 12–18 mm in length (McGregor et al. 1986), moderately reflexed (Lesica 2012).

Fruit: Legume ascending, ovoid, 4-8 mm in length, silky-haired, hidden among leaves (Lesica 2012); seeds smooth and brown, 2.5-3 mm in length (McGregor et al. 1986).

(Lesica's contribution adapted from Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.)

  • Literature Cited AboveLegend:   View Online Publication
    • Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • McGregor, R.L., coordinator, and T.M. Barkley, R.E. Brooks, and E.K. Schofield, eds.: Great Plains Flora Association. 1986. Flora of the Great Plains. Lawrence, KS: Univ. Press Kansas. 1392 pp.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • 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.
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Citation for data on this website:
Summer Milkvetch — Astragalus hyalinus.  Montana Field Guide.  .  Retrieved on , from