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Montana Field Guide

Montana Field Guides

Sandweed - Athysanus pusillus

Species of Concern
Native Species

Global Rank: G5
State Rank: S1S2
(see State Rank Reason below)
State Threat Score: High
CCVI: Highly Vulnerable

Agency Status
USFS: Sensitive - Known in Forests (BRT, KOOT)
Sensitive - Suspected in Forests (LOLO)



External Links

State Rank Reason (see State Rank above)
Known in Montana from a limited area of the Bitterroot Mountains. Only three occurrences have a large number of indivuals and several occurrences have populations of spotted knapweed and/or cheatgrass established. Invasive weeds may threaten the long-term viability of the species in Montana.
  • Details on Status Ranking and Review
    Sandweed (Athysanus pusillus) Conservation Status Review
    Review Date = 05/06/2013
    View State Conservation Rank Criteria
    Population Size

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

    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

    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.

    CommentTrends are unknown, though may be declining due to impacts to habitat quality, particularly from invasive species.


    Score2-3 - High to Very High.

    Intrinsic Vulnerability

    Score1-2 - Moderate to High Vulnerability.

    Raw Conservation Status Score

    Score 11 to 14 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Sandweed is an annual with slender stems, up to 15 cm tall, that are simple or sparingly branched from near the base. The alternate, lance-shaped leaves, 6-20 mm long, have toothed margins and are stalked below but sessile above. Foliage is covered with simple and branched hairs. Miniscule white flowers are born on short, spreading stalks in open, unbranched inflorescences at the ends of the stems. The four white petals are ca. 2 mm long, and the sepals are only 1 mm long. The broadly pear-shaped fruits, 2-3 mm long, are covered with hooked hairs and borne on reflexed stalks.

Flowering in April-May.

Diagnostic Characteristics
The annual habit and drooping, pear-shaped fruits covered with hooked hairs make this species distinctive.

Species Range
Montana Range Range Descriptions


Range Comments
S. B.C. to CA, east to MT, ID, and UT. Peripheral.

Observations in Montana Natural Heritage Program Database
Number of Observations: 30

(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)

Vernally moist, shallow soil of steep slopes and cliffs in the lower montane zone.
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Ecological Systems Associated with this Species

Threats or Limiting Factors
Reported threats to Montana's population of Sandweed refer to populations where non-native plants are established (MTNHP Threat Assessment 2021). Sandweed is restricted to small areas of open habitat where direct competition with Cheatgrass (Bromus tectorum) and Spotted Knapweed (Centaurea stoebe) is likely to lower plant viability.

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
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Citation for data on this website:
Sandweed — Athysanus pusillus.  Montana Field Guide.  .  Retrieved on , from