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Montana Field Guide

Montana Field Guides

Silky prairie clover - Dalea villosa
Other Names:  Petalostemon villosus

Species of Concern
Native Species

Global Rank: G5
State Rank: S2
(see State Rank Reason below)

Agency Status
MNPS Threat Rank:

External Links

State Rank Reason (see State Rank above)
In Montana, known from a few, small occurrences in the extreme eastern portion of the state. Current population levels and trends are unknown.
  • Details on Status Ranking and Review
    Silky prairie clover (Dalea villosa) Conservation Status Review
    Review Date = 04/24/2013
    View State Conservation Rank Criteria
    Population Size

    Score3 - Vey Small: Generally <2,000 individuals.

    Range Extent

    Score1 - Peripheral, Disjunct or Sporadic Distribution in MT: Widespread species that is peripheral, disjunct or sporadically distributed within MT such that it occurs in <5% of the state (<7,500 sq. miles or the combined area of Beaverhead and Ravalli Counties) or is restricted to 4-5 sub-basins.

    Area of Occupancy

    Score2 - Low: Generally occurring in 4-10 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).


    Score0-3 - Population trends are unknown.



    Score1-2 - Medium to High.

    CommentThreats are poorly documented though 3 sites occur along sandy roadsides, which could result in some adverse impacts. Conversely, there are no known threats that are high in magnitude.

    Intrinsic Vulnerability

    Score0-1 - Low to Moderate Vulnerability.

    Raw Conservation Status Score

    Score 9 to 14 total points scored out of a possible 19.

General Description
Silky Prairie Clover is a perennial herb with ascending or lax, branched stems that are 20-35 cm high sometimes resembling a shrub form, and which arise from red-orange roots and a rootcrown. The alternate, pinnately compound leaves are 2-4 cm long and have 11-21 linear leaflets. The foliage has numerous sunken glands and is densely long and hairy. The pink to rose-purple flowers are densely crowded in cylindrical spikes that are 3-12 cm long, at the ends of stems and branches. Each flower is 4-6 mm long and has 4 separate petals, a densely spreading, hairy, 5-lobed, cup-shaped calyx, and 5 stamens that are usually longer than the petals. The narrowly egg-shaped pods are 2-3 mm long and densely long and hairy.

Flowering in late June-early August.

Diagnostic Characteristics
Other Dalea in Montana usually have <13 leaflets and are not as conspicuously hairy. The combination of the long, hairy calyx and 5 stamens further separate this species from other species of Dalea and from species of Psoralea and Amorpha.

Species Range

Range Comments
Silky prairie clover is a Great Plains species known from Saskatchewan, Manitoba and Wisconsin south to New Mexico, Texas and Oklahoma.

Observations in Montana Natural Heritage Program Database
Number of Observations: 7

(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 soils of prairies and open woodlands often near sandstone outcrops or on dunes and roadsides. Sites are typically sparsely-vegetated. Common associated species include Calamovilfa longifolia, Andropogon hallii and Stipa comata.

Ecological Systems Associated with this Species

Mainatin early successional, sandy habitats. Avoid direct impacts to populations and associated habitat. Avoid broadcast spraying of herbicides in the vicinity of populations; use care with spot spraying.

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Citation for data on this website:
Silky prairie clover — Dalea villosa.  Montana Field Guide.  .  Retrieved on , from