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Painted Milkvetch - Astragalus ceramicus var. apus

Species of Concern

Global Rank: G4T3
State Rank: S1S2
* (see State Rank Reason below)

Agency Status
MNPS Threat Rank: 2

External Links

State Rank Reason (see State Rank above)
Painted milkvetch is known only from the upper Snake River Plains of southeast Idaho and adjacent Montana, where it is restricted to the Centennial Valley of Beaverhead County. The disruption of natural disturbance regimes, including fire, ungulate grazing and pocket gopher activity, can lead to dune stabilization, reducing the extent of blowout areas with early successional vegetation, upon which this species depends. Portions of its habitat lie on private or public lands without sensitive species management policies in place.
  • Details on Status Ranking and Review
    Painted Milkvetch (Astragalus ceramicus var. apus) Conservation Status Review
    Review Date = 04/24/2013
    View State Conservation Rank Criteria
    Population Size

    Score1-2 - Small to Moderate. Population size is imprecisely known but is believed to be >2,000 individuals and <100,000 individuals.

    CommentAvailable data on population levels are limited. Additional information needed.

    Range Extent

    Score3 - Local Endemic or Very Small Montana Range: Generally restricted to an area <10,000 sq. miles (equivalent to the combined area of Phillips and Valley Counties) or <6 Sub-basins (4th code watersheds) Range-wide OR limited to one Sub-basin in Montana

    CommentVery small Montana range.

    Area of Occupancy

    Score3 - Very Low: Generally occurring in 3 or fewer Subwatersheds (6th Code HUC’s).

    Environmental Specificity

    Score2 - High: Species is restricted to a highly specialized and limited habitat and is typically dependent upon unaltered, high-quality habitat (C Values of 8-10).


    ScoreNA - Rank factor not assessed.

    CommentTrend data are lacking, though there is no indication that the species' has experienced significant declines in Montana.


    Score1-2 - Medium to High.

    Intrinsic Vulnerability

    Score1 - Moderate Vulnerability: Specific biological attributes, unusual life history characteristics or limited reproductive potential makes the species susceptible to extirpation from stochastic events or other adverse impacts to its habitat and slow to recover.

    Raw Conservation Status Score

    Score 11 to 13 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Painted Milkvetch is a slender, wiry, herbaceous perennial with trailing or ascending stems, 3-20 cm long, arising from long, widely spreading, rhizome-like rootcrown branches. Alternate, pinnately compound leaves are 2-17 cm long and have 1-4 pairs of narrow, stem-like, lateral leaflets. Foliage is sparsely covered with unbranched, short, white hairs. Flower stalks are 2-8 cm long, each with 2-15 widely-spaced flowers. The white, pea-like flowers have an erect upper petal, 6-11 mm long, and a calyx, 3-6 mm long, sparsely covered with long white or black hairs. Egg-shaped, inflated fruits, 15-50 mm long, are mottled purple and green. They often lie on the ground like miniature balloons that pop when squeezed or stepped on.

Flowering occurs from late June into July.

Diagnostic Characteristics
The purple-mottled, inflated fruits combined with linear leaflets are diagnostic traits for Astragalus ceramicus. Variety apus has sessile (stalkless) pods, whereas variety filifolius, found in eastern Montana, has pods on a short stalk coming out of the calyx.

Species Range

Range Comments
Se. Idaho and extreme sw. Montana. Regional endemic.

Observations in Montana Natural Heritage Program Database
Number of Observations: 4

(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)

The species is associated with early successional habitats in sandhills (Schassberger 1988). It is found in sandy, well-drained blowout areas and sandy flats or draws of old sand dunes at elevations of 6650-6700 feet, on moderately steep (20-30%), south- and west-facing slopes. Much of the vegetative cover consists of Artemisia tripartita, Phacelia hastata, Agropyron dasystachyum, Stipa comata and Tetradymia canescens.

Ecological Systems Associated with this Species

Painted milkvetch occurs in the sand dune region of the Centennial Valley where there is light to moderate grazing pressure (Culver 1993). It requires the open sand of early successional areas, and suitable habitat may be reduced when plant succession leads to later stages in which vegetation covers areas of formerly open sand (Lesica and Cooper 1998). Historically, the diversity of sandhills plant communities was maintained by a fire cycle of 20-30 years. The activity of pocket gophers (Thomomys talpoides) also appears to be an important force in initiating blowouts and maintaining early seral vegetation (Lesica and Cooper 1998).

In 1987, the populations in the Centennial Sandhills were reported to be thriving; however in 1993, Culver observed only a few small populations, suggesting that the number of above-ground stems may vary from year to year.

The removal of natural disturbance regimes, including fire, ungulate grazing and pocket gopher activity, leads to dune stabilization and reduces the extent of early seral blowout vegetation areas upon which this species depends. Painted milkvetch would benefit from restoration of the fire regime and moderate grazing, at least in years following burns. Severe destabilization of the dunes, e.g., from off-road vehicle use, could also threaten its habitat.

  • Additional ReferencesLegend:   View Online Publication
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    • Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.
    • Culver, D.R. 1993. Sensitive plant species inventory in the Centennial Valley, Beaverhead County, Montana. Unpublished report to the Butte District, Bureau of Land Management. Montana Natural Heritage Program, Helena, 42 pp. plus appendices.
    • Lesica, P. & S. V. Cooper. 1998. Succession and disturbance in sandhills vegetation: constructing models for managing biological diversity. Conservation Biology 13:293-302.
    • Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Schassberger, L.A. 1987. The ecology of Astragalus ceramicus var. APUS in relation to succession in the Centennial Sandhills of southwestern Montana. [Progress report to The Nature Conservancy].
    • Schassberger, L.A. 1988. Effects of grazing on the habitat of Astragalus ceramicus var. Apus in the sandhills of the Centennial Valley, Montana. M.A. thesis. University of Montana, Missoula, Montana.
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Citation for data on this website:
Painted Milkvetch — Astragalus ceramicus var. apus.  Montana Field Guide.  .  Retrieved on , from