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Astragalus aquilonius

(Barneby) Barneby

Lemhi Milkvetch

G3Vulnerable Found in 1 roadless area NatureServe Explorer →
G3VulnerableGlobal Rank
MediumThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.132276
Element CodePDFAB0F0Q0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderFabales
FamilyFabaceae
GenusAstragalus
Other Common Names
Lemhi milkvetch (EN)
Concept Reference
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-04-04
Change Date1986-07-14
Edition Date2025-04-04
Edition AuthorsStoner, N.(1993), rev. J. Beckman (3/96), rev. Johnson, J. (2025)
Threat ImpactMedium
Range Extent5000-20,000 square km (about 2000-8000 square miles)
Number of Occurrences21 - 80
Rank Reasons
Astragalus aquilonius is a short-lived perennial herb that is endemic to east-central Idaho found on unstable soils within shrub-steppe zones in the Upper Salmon and Lower Lemhi River watersheds. Its populations are variable, and threat impacts are poorly understood but include livestock grazing, wildfire, and invasive plant species.
Range Extent Comments
Astragalus aquilonius occurs in the western United States, where it is known from the Upper Salmon River near Challis and disjunctly from along the lower Lemhi River in Custer, Butte, and Lemhi counties, Idaho (Spahr et al. 1991). Range extent was estimated using herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 1994 and 2025 (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025, CPNWH 2025).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are 40 occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025, CPNWH 2025).
Threat Impact Comments
Riparian habitats are grazed heavily by livestock on the Salmon-Challis National Forest, and the condition of many of these habitats is declining due to trampling, compaction, and loss of groundwater (K. Baumann pers. comm. 2025). The habitats have potential for wildfire, but generally have a low fuel load. Cheatgrass is invading, especially near roads (SIRPWG 2016).
Ecology & Habitat

Habitat

Astragalus aquilonius grows in gullies on clay bluffs, steep eroded banks in canyons, sand or gravel bars along streams, on shale, clay, or alluvial debris, with shadscale or sagebrush (FNA 2023). One population is found on a dry, gravelly ridge with scattered Douglas-fir (SIRPWG 2016).
Terrestrial Habitats
Shrubland/chaparralDesertBarrens
Palustrine Habitats
Riparian
Other Nations (1)
United StatesN3
ProvinceRankNative
IdahoS3Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
2.3 - Livestock farming & ranchingLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
7 - Natural system modificationsRestricted (11-30%)UnknownModerate (short-term)
7.1 - Fire & fire suppressionRestricted (11-30%)UnknownModerate (short-term)
8 - Invasive & other problematic species, genes & diseasesSmall (1-10%)UnknownHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesSmall (1-10%)UnknownHigh (continuing)

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Plant Characteristics
DurationPERENNIAL, Short-lived
Economic Value (Genus)Yes
Roadless Areas (1)
Idaho (1)
AreaForestAcres
Lemhi RangeSalmon-Challis National Forest308,533
References (12)
  1. Baumann, Katie, Plant Biologist, Salmon-Challis National Forest. 2025. Emails regarding the status and trends of certain rare plant species on the Salmon-Challis National Forest.
  2. Consortium of Pacific Northwest Herbaria (CPNWH). 2025. Online database of vascular plant specimens from the Pacific Northwest. Online. Available: http://www.pnwherbaria.org/index.php (accessed 2025).
  3. Flora of North America Editorial Committee (FNA). 2023. Flora of North America north of Mexico. Vol. 11. Magnoliophyta: Fabaceae, parts 1+2. Oxford Univ. Press, New York. xxvii + 1108 pp.
  4. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  5. Idaho Native Plant Society. 1992. Federal candidate (C1 and C2) and listed rare plants of Idaho. unpaginated.
  6. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  7. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  8. NatureServe. 2025. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  9. NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2024. Version: 1.1.1 (released Oct 01, 2024).
  10. Southern Idaho Rare Plant Working Group (SIRPWG). 2016. Ranking files and spreadsheets presented to the 2016 Idaho Rare Plant Conference.
  11. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).
  12. Spahr, R., L. Armstrong, D. Atwood, and M. Rath. 1991. Threatened, endangered, and sensitive species of the Intermountain Region. U.S. Forest Service, Intermountain Region, Ogden, UT.