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Astragalus subcinereus

Gray

Silver Milkvetch

G3Vulnerable (G3G4) Found in 1 roadless area NatureServe Explorer →
G3VulnerableGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.146358
Element CodePDFAB0F8L0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single nation
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderFabales
FamilyFabaceae
GenusAstragalus
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.
Taxonomic Comments
While varieties are not recognized as distinct from the species Astragalus subcinereus by Kartesz (1994 or 1999), the Flora of North America Editorial Committee (FNA 2023, vol. 11) includes three varieties: A. subcinereus var. basalticus, A. subcinereus var. sileranus, and A. subcinereus var. subcinereus.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2026-01-14
Change Date2026-01-14
Edition Date2026-01-14
Edition AuthorsA. Olivero (2002), rev. Soteropoulos (2026)
Threat ImpactUnknown
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences21 - 300
Rank Reasons
Astragalus subcinereus is a perennial herb found in ponderosa pine, white fir, aspen, oak, pinyon-juniper, sagebrush, and mixed mountain brush communities. It occurs in the southwestern United States in northwestern Arizona, southeastern Nevada, and southern Utah. There are at least 80 occurrences, which face threats from grazing, solar energy development and mineral extraction, road maintenance, drought, and climate change. Monitoring of populations should be conducted to improve our understanding of reproduction, plant abundance, threats, and trends, as well as continuing conservation measures to protect the taxon.
Range Extent Comments
Astragalus subcinereus occurs in the southwestern United States in northwestern Arizona (Coconino, Mohave, and Yavapai counties), southeastern Nevada (Lincoln County), and southern Utah (Emery, Garfield, Iron, Kane, Sevier, and Washington counties) (FNA 2023). Range extent was estimated to be over 70,000 square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025 (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026). There are three varieties, some of which have overlapping distribution; see each of the varieties for more information.
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 80 occurrences rangewide (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026).
Threat Impact Comments
Threats for this species and its varieties are not well documented, with the most information available for A. subcinereus var. basalticus. Threats include grazing, solar energy development and mineral extraction, and road maintenance (UNHP 2024), as well as drought and climate change (Wrobleski 2023).
Ecology & Habitat

Habitat

Astragalus subcinereus grows in ponderosa pine, white fir, aspen, oak, pinyon-juniper, sagebrush, and mixed mountain brush communities (FNA 2023).

Reproduction

This taxon flowers from May to September (FNA 2023).
Terrestrial Habitats
Forest/WoodlandForest - ConiferWoodland - ConiferShrubland/chaparral
Other Nations (1)
United StatesN3
ProvinceRankNative
UtahSNRYes
NevadaS2Yes
ArizonaSNRYes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureUnknownUnknownHigh (continuing)
2.3 - Livestock farming & ranchingUnknownUnknownHigh (continuing)
2.3.4 - Scale unknown/unrecordedUnknownUnknownHigh (continuing)
3 - Energy production & miningUnknownUnknownHigh (continuing)
3.1 - Oil & gas drillingUnknownUnknownHigh (continuing)
3.3 - Renewable energyUnknownUnknownModerate - low
4 - Transportation & service corridorsUnknownUnknownHigh (continuing)
4.1 - Roads & railroadsUnknownUnknownHigh (continuing)
11 - Climate change & severe weatherPervasive (71-100%)UnknownHigh (continuing)
11.2 - DroughtsPervasive (71-100%)UnknownHigh (continuing)

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Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)Yes
Roadless Areas (1)
Utah (1)
AreaForestAcres
Casto BluffDixie National Forest87,466
References (13)
  1. Barneby, R.C. 1964. Atlas of North American Astragalus. 2 Vols. New York Botanical Garden, Bronx, New York. 1188 pp.
  2. 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.
  3. Global Biodiversity Information Facility (GBIF). 2026. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2026).
  4. iNaturalist. 2026. Online. Available: https://www.inaturalist.org (accessed 2026).
  5. Isely, D. 1998. Native and naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). Monte L. Bean Life Science Museum, Brigham Young University; MLBM Press, Provo, Utah. 1007 pp.
  6. 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.
  7. Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.
  8. Kearney, T.H., R.H. Peebles, J.T. Howell, and E. McClintock. 1960. Arizona Flora. Revised 2nd Edition with supplement. University of California Press, Berkeley, California. 1085 pp.
  9. NatureServe. 2026. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  10. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  11. Southwest Environmental Information Network (SEINet). 2026. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2026).
  12. Utah Natural Heritage Program (UNHP). 2024. Utah Rare Plant Database (accessed 2024).
  13. Wrobleski, A., Ernst, S., Weber, T., and A. Delach. 2023. The impact of climate change on endangered plants and lichen. PLOS Climate 2(7): e0000225.