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Montana Field Guide

Montana Field Guides

Woolly Twinpod - Physaria didymocarpa var. lanata

Species of Concern
Native Species

Global Rank: G5T2
State Rank: S2S3
(see State Rank Reason below)
State Threat Score: No Known Threats

Agency Status
USFS: Species of Conservation Concern in Forests (CG)


External Links

State Rank Reason (see State Rank above)
Only a few known occurrences in Montana, including two potentially large populations. However, lots of unsurveyed potential habitat exists. Both BLM and private lands are important to the viability of the species in Montana. Oil and gas development, coalbed methane, and invasive weeds have the potential to detrimentally impact populations.
  • Details on Status Ranking and Review
    Woolly Twinpod (Physaria didymocarpa var. lanata) Conservation Status Review
    Review Date = 04/06/2012
    View State Conservation Rank Criteria
    Population Size

    Score2-3 - Very Small to Small: Population size is imprecisely known but is believed to be <10,000 individuals.

    CommentPopulation estimates are imprecise but available data support a minimum size of at least several hundred plants upwards of a couple thousand plants.

    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 southeast Montana and adjacent Wyoming

    Area of Occupancy

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

    Environmental Specificity

    Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).

    CommentSpecific habitat requirements unclear, though does not appear to be restricted to very narrow conditions, nor to uncommon habitats.


    ScoreNA - Rank factor not assessed.

    CommentTrends are unknown.


    Score1-2 - Medium to High.

    CommentPotential for negative impacts from oil and gas development and invasive weeds have been identified.

    Intrinsic Vulnerability

    Score0-1 - Low to Moderate Vulnerability.

    CommentDegree of intrinsic rarity uncertain.

    Raw Conservation Status Score

    Score 8 to 11 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Woolly Twinpod is a perennial herb with numerous ascending stems that are ca. 1 dm long and arising from a basal rosette surmounting a branched crown and large taproot. The basal leaves are 15-40 mm long and are spoon-shaped with broad-toothed margins and long petioles. The alternate stem leaves are broadly lance-shaped with mostly entire margins. Foliage is covered with silvery, tangled, and spreading hairs. The yellow, stalked flowers are borne at the tops of the stems in a narrow inflorescence that elongates as the fruit matures. Each flower has 4 separate petals that are 9-12 mm long and 4 separate sepals. The ascending, inflated fruits are 7-20 mm tall and at least as wide and are 2-lobed with the lobes more equally defined above and below. There are 4 ovules in each of the 2 chambers. The style is 7-9 mm long.

Flowering and fruiting May-June.

Diagnostic Characteristics
There are many similar-appearing Physaria species; a technical manual and hand lens or microscope will be required for positive identification. The long, tangled spreading hairs on the leaves, especially at the base, help separate this from other species.

Wooly Twinpod - Physaria didymocarpa var. lanata, SOC
*Pedicels are spreading, straight, or sigmoid, 3-12 mm long.
*Fruits inflated and 2-lobed, 7-20 mm tall, and with 2-4 ovules per locule [Count the stalk of the ovules.]
*Basal Leaves obovate in shape with entire to coarsely dentate margins.

Sharpleaf twinpod - Physaria acutifolia
*Pedicels are spreading, straight, or sigmoid, 5-10 mm long.
*Fruits inflated and 2-lobed, 6-10 mm wide, and with 2 ovules per locule.
*Basal leaves ovate to obovate in shape and usually entire.

Thick-leaf BladderpodPhysaria pachyphylla, SOC
*Pedicels curve upwards (ascend), 3-10 mm long.
*Fruits inflated, not 2-lobed, and narrowly elliptic to ovoid, 3-6 mm tall. Style is more than half the length of the fruit (silicle).
*Basal leaves have distinct petioles and blades. Blades are spatulate to oblanceolate in shape, nearly 1 mm thick and cupped (but not folded), and with entire margins [key characteristic].
*Plants grow on pinkish or reddish soils derived from limestone on exposed slopes and ridges in valleys.

Species Range
Montana Range Range Descriptions


Range Comments
Regional endemic of north-central Wyoming and adjacent Montana.

Observations in Montana Natural Heritage Program Database
Number of Observations: 15

(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, often calcareous soil of open grassland or shrubland slopes in the plains.
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
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Fertig, W. 2000. State Species Abstract: Physaria didymocarpa var. lanata. Wyoming Natural Diversity Database, Laramie, Wyoming. 2 pages.
    • 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.
    • Taylor, A. and R. Caners. 2002. Baseline Survey for Astragalus barrii Barneby (Barr's milkvetch) and Physaria didymocarpa var. lanata A. Nels. (woolly twinpod) in eastern Big Horn and southwestern Rosebud Counties, Montana. Montana Natural Heritage Program, Helena, Montana. 27 pp.
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Citation for data on this website:
Woolly Twinpod — Physaria didymocarpa var. lanata.  Montana Field Guide.  .  Retrieved on , from