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Silky prairie clover - Dalea villosa
Other Names:
Petalostemon villosus
State Rank Reason (see State Rank above)
DRAFT: Requesting feedback on the 2026 revised rank, factors, and State Rank Reason outlined below and in the Conservation Status Rank Report.
Dalea villosa is known from extreme, eastern Montana, where it occurs in sandy prairie sites at the western edge of its distrubition. It has only been documented from about a half dozen sites and all occurrences appear to be relatively small in size and extent. Trends are unknown, though the species' habitat is generally intact and in good condition. Significant or potential threats have not been documented besides the potential, negative impacts that 2 occurrences could experience as a result of being along roadsides.
Surveys are needed at a few sites to assess population sizes and extent, habitat quality and potential theats. Monitoring of at least several populations is needed to be able to assess potential population trends.
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.
Phenology
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
Montana Range
Range Descriptions
Native
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: 11
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
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.
National Vegetation Classification System Groups Associated with this Species
Grassland
Lowland - Prairie Grassland
Ecology
POLLINATORS The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap:
Bombus auricomus,
Bombus pensylvanicus,
Bombus griseocollis, and
Bombus impatiens (Colla and Dumesh 2010, Williams et al. 2014).
Management
Maintain 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.
Stewardship Responsibility
Threats or Limiting Factors
STATE THREAT SCORE REASON
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).
References
- Literature Cited AboveLegend:
View Online Publication
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.- MTNHP Threat Assessment. 2021. State Threat Score Assignment and Assessment of Reported Threats from 2006 to 2021 for State-listed Vascular Plants. Botany Program, Montana Natural Heritage Program, Helena, Montana.
- 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?- Anderson, N.L. 1951. Field studies on the biology of range grasshoppers of southeastern Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 96 p.
- 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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