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Montana Field Guides

Low Milkweed - Asclepias pumila

Native Species

Global Rank: G5
State Rank: S3S4
(see State Rank Reason below)
C-value: 5

Agency Status


External Links

State Rank Reason (see State Rank above)
Asclepias pumila is found scattered through half of eastern Montana.
  • Details on Status Ranking and Review
    Low Milkweed (Asclepias pumila) Conservation Status Review
    Review Date = 11/14/2016
    View State Conservation Rank Criteria
    Range Extent

    ScoreF - 20,000-200,000 sq km (~8,000-80,000 sq mi)

    Area of Occupancy

    ScoreD - 6-25 4-km2 grid cells

    Number of Populations

    ScoreB - 6 - 20

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

    ScoreU - Unknown

    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

    ScoreC - Not intrinsically vulnerable

General Description
Plants: Rhizomatous. Stems simple or branched at the base, 5–20 cm. Herbage glabrous to puberulent (Lesica 2012).

Leaves: Leaves crowded, alternate and spiraling tightly around stem, or whorled near the stem's base (McGregor et al. 1986); blades erect or spreading, filiform, 1–5 cm long (Lesica 2012), 0.5-1(1.5) mm wide, leathery, apex acute; margins closely rolled under; base sessile and narrowly acute (McGregor et al. 1986).

Inflorescence: 1 to many umbels in axils of upper leaves (McGregor et al. 1986), each with 5 to 20 flowers; peduncles 5–10 mm in length (Lesica 2012); pedicels threadlike, puberulent, and 4-12 mm in length (McGregor et al. 1986).

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

Flowers July-September (McGregor et al. 1986).

Species Range
Montana Range Range Descriptions


Range Comments
MT, ND south to NM, TX and IA (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 52

(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)

Gypseous or stony calcareous soils (McGregor et al. 1986) of grasslands and plains (Lesica 2012).

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

The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus huntii, Bombus rufocinctus, Bombus ternarius, Bombus terricola, Bombus pensylvanicus, Bombus bimaculatus, Bombus griseocollis, Bombus impatiens, Bombus insularis, and Bombus flavidus (Plath 1934, Heinrich 1976, Thorp et al. 1983, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014, Tripoldi and Szalanski 2015).

Reproductive Characteristics
Flowers: Flowers 5–8 mm high; sepals villous, ca 2 mm long (Lesica 2012), green or shaded with purple; petals white or tinged with pink or yellow-green, particularly on the outer surface, oval to elliptic (McGregor et al. 1986), glabrous, 3–4 mm long; gynostegium greenish-white, glabrous, 1–1.5 mm high (Lesica 2012), stipitate; column 0.6-1.1 mm high and 0.7-0.9 mm in width (McGregor et al. 1986); hoods 1–2 mm in length, oblong (Lesica 2012), upright, connected near base, widely rounded at apex, margins smooth (McGregor et al. 1986); horns exserted (Lesica 2012), arching above head of anther, 1.5-2 times the length of hood; corpusculum about 0.2 mm in length; pollinia about 0.8 mm in length (McGregor et al. 1986).

Fruit: Follicles erect to ascending, fusiform, smooth, puberulent, 4–8 cm long (Lesica 2012), 6-8 mm thick; pedicels straight to sharply bent; seeds 4-6 mm in length, ovate, with a tuft of soft white to tan hairs (coma) 12-26 mm in length (McGregor et al. 1986).

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

This species is toxic to farm animals (McGregor et al. 1986).

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S., L. Richardson, and P. Williams. 2011. Bumble bees of the eastern United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 103 p.
    • 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.
    • McGregor, R.L. (coordinator), T.M. Barkley, R.E. Brooks, and E.K. Schofield (eds). 1986. Flora of the Great Plains: Great Plains Flora Association. Lawrence, KS: Univ. Press Kansas. 1392 pp.
    • Plath, O.E. 1934. Bumblebees and their ways. New York, NY: Macmillan Company. 201 p.
    • 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.
    • Tripoldi, A.D. and A.L. Szalanski. 2015. The bumble bees (Hymenoptera: Apidae: Bombus) of Arkansas, fifty years later. Journal of Melittology 50: doi:
    • 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?
    • Britton, N. L. and A. B. Brown. 1913. An Illustrated Flora of the Northern United States, Canada, and the British Possessions. 2nd Edition in 3 Volumes. New York, NY: Charles Scribner's Sons. B13BRI01PAUS.
    • Fritzen, D.E. 1995. Ecology and behavior of Mule Deer on the Rosebud Coal Mine, Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 143 p.
    • Rennick, R.B. 1981. Effects of prescribed burning on mixed prairie vegetation in southeastern Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 144 p.
    • Skilbred, Chester L. 1979. Plant succession on five naturally revegetated strip-mined deposits at Colstrip, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 128 pp.
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Citation for data on this website:
Low Milkweed — Asclepias pumila.  Montana Field Guide.  .  Retrieved on , from