S. Wats.
Identity
Unique IDELEMENT_GLOBAL.2.132971
Element CodePDFAB0F6C0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
IUCNLeast concern
Endemicendemic to a single nation
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderFabales
FamilyFabaceae
GenusAstragalus
Other Common Namesegg milkvetch (EN) Egg Milkvetch (EN)
Concept ReferenceKartesz, 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 Date2026-03-11
Change Date1988-08-31
Edition Date2026-03-11
Edition AuthorsSoteropoulos (2026)
Threat ImpactUnknown
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences81 - 300
Rank ReasonsAstragalus oophorus is a wide-ranging perennial herb found in a variety of xeric, open habitats, including sagebrush and bitterbrush communities, mixed desert shrub communities, ponderosa pine forests, pinyon pine, pinyon-juniper, oak, and mountain brush communities . It is endemic to the southwestern United States from eastern California, east to western Colorado, and south to New Mexico and Arizona. There are over 200 occurrences, which face threats from commercial development, grazing, lithium extraction, wind farm development, road construction and maintenance, military activities, recreational activities (including off-road vehicles, hiking, skiing, mountain biking, and camping) and development, fire suppression, exotic plant species, and trampling by feral horses and burros. Little is known about trends, but with a large range extent and large number of occurrences, abundant habitat, and broad habitat preferences, this species is considered apparently secure.
Range Extent CommentsAstragalus oophorus is endemic to the southwestern United States from eastern California, east to western Colorado, and south to New Mexico and Arizona (FNA 2023). Range extent was estimated to be over 500,000 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).
Occurrences CommentsBy 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 over 200 occurrences rangewide (RARECAT 2025, GBIF 2026, iNaturalist 2026, NatureServe 2026, SEINet 2026).
Threat Impact CommentsAlthough threats at the species-level are not widely documented, varieties of this species face threats from commercial development, grazing and associated habitat loss and soil disturbance, lithium extraction, wind farm development, road construction and maintenance, military activities, recreational activities (including off-road vehicles, hiking, skiing, mountain biking, and camping) and development, fire suppression, exotic plant species (including cheatgrass (Bromus tectorum) and red brome (Bromus rubens)), and trampling by feral horses and burros (Smith 2001, Clifford et al. 2025, NatureServe 2026). Potential threats include fruit and seed predation by insects or rodents as well as climactic shifts, such as extreme heat, cold, or drought, and historical threats of nuclear testing, which could resume and cause future impacts (Smith 2001). However, there is insufficient data, including anecdotal accounts, to understand scope and severity of threats for this species rangewide (NatureServe 2026).