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Astragalus conjunctus

S. Wats.

Stiff Milkvetch

G4Apparently Secure Found in 3 roadless areas NatureServe Explorer →
G4Apparently SecureGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.129617
Element CodePDFAB0F2C0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single nation
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderFabales
FamilyFabaceae
GenusAstragalus
Other Common Names
Idaho Milkvetch (EN) Idaho 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.
Taxonomic Comments
Comprised of two varieties (Kartesz 1999).
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2024-12-31
Change Date2001-01-31
Edition Date2024-12-31
Edition AuthorsEberly (2024)
Threat ImpactUnknown
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences81 - 300
Rank Reasons
Astragalus conjunctus is a perennial herb of the northwestern United States that is known from Idaho, Oregon, and western Idaho (Owyhee County). Two varieties (conjunctus and rickardii) are recognized; see each for additional information. Multiple threats related to recreational activities, non-native plants, and grazing potentially impact the taxon. Additional surveys would increase knowledge of abundance, response to threats, and current vs. historical distribution.
Range Extent Comments
Astragalus conjuctus occurs in the northwestern United States in Idaho, Oregon, and Washington. Astragalus conjunctus var. conjunctus occurs in central and eastern Oregon and western Idaho (Owyhee County) and Astragalus conjunctus var. rickardii is endemic to the Columbia Plateau of north-central Oregon (Wasco County) and south-central Washington (Benton County) (Welsh et al. 1997, Beck and Caplow 2006, Myers et al. 2020). Range extent was estimated using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1983 and 2024 (CPNH, 2024, GBIF 2024, iNaturalist 2024, NatureServe 2024, SEINet 2024).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1983 and 2024, it is estimated that there are over 146 occurrences rangewide (CPNH, 2024, GBIF 2024, iNaturalist 2024, NatureServe 2024, SEINet 2024). There may be an additional 100 occurrences based on historical records (prior to 1983), but these locations need to be surveyed to determine if habitat and plants remain. It may suggest that the species is more common than recent records show.
Threat Impact Comments
See each variety for additional information. Threats reported for A. conjunctus var. rickardii include trampling by hunters and hikers, grazing, and exotic weeds (NatureServe 2024). Fire may be a threat, but the plants tolerance to fire is unknown.
Ecology & Habitat

Habitat

This species grows in grasslands, bunchgrass prairie, bunchgrass-sagebrush, and bunchgrass-scabland communities and along roadsides, sometimes on basalt bedrock (Welsh et al. 1997, Beck and Caplow 2006, Myers et al. 2020, NatureServe 2024).
Terrestrial Habitats
Forest EdgeShrubland/chaparralGrassland/herbaceousDesert
Other Nations (1)
United StatesN4
ProvinceRankNative
OregonSNRYes
WashingtonSNRYes
IdahoS2Yes
WyomingSNRYes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquacultureUnknownUnknownHigh (continuing)
2.3 - Livestock farming & ranchingUnknownUnknownHigh (continuing)
2.3.1 - Nomadic grazingUnknownUnknownHigh (continuing)
6 - Human intrusions & disturbanceUnknownUnknownHigh (continuing)
6.1 - Recreational activitiesUnknownUnknownHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesUnknownUnknownHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesUnknownUnknownHigh (continuing)
8.1.1 - Unspecified speciesUnknownUnknownHigh (continuing)

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Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)Yes
Roadless Areas (3)
Oregon (3)
AreaForestAcres
Metolius BreaksDeschutes National Forest11,141
Myrtle SilviesMalheur National Forest11,679
Rock CreekOchoco National Forest11,396
References (9)
  1. Beck, K.A., and F. Caplow. 2006. Additions to the Vascular Flora Of Washington from a Biodiversity Study on the Hanford Nuclear Reservation. Madroño 53:36-45.
  2. Consortium of Pacific Northwest Herbaria (CPNH). 2024. Specimen Database. Online. Available: http://www.pnwherbaria.org/data/search.php (accessed 2024).
  3. Global Biodiversity Information Facility (GBIF). 2024. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2024).
  4. iNaturalist. 2024. Online. Available: https://www.inaturalist.org (accessed 2024).
  5. 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.
  6. Meyers, S.C., T. Jaster, K.E. Mitchell, T. Harvey, and L.K. Hardison, editors. 2020. Flora of Oregon. Volume 2: Dicots A-F. Botanical Research Institute of Texas, Fort Worth, TX. 861 pp.
  7. NatureServe. 2024. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  8. Southwest Environmental Information Network (SEINet). 2024. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2024).
  9. Welsh, S.L., F. Caplow, and K. Beck. 1997. New variety of <i>Astragalus conjunctus</i> S. Watson from Benton County, Washington. Great Basin Naturalist 57(4):352-354.