Taxon Report

Astragalus rattanii Gray var. jepsonianus Barneby

Jepson's milk-vetch

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Taxon Summary

Astragalus rattanii var. jepsonianus, commonly known as Jepson's milk-vetch, is a annual herb in the Fabaceae that is found only in California. It occurs within Chaparral, Cismontane woodland, and Valley and foothill grassland, growing at elevations from 295 to 700 meters. Astragalus rattanii var. jepsonianus is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

  Classification
Scientific Name:
 Astragalus rattanii Gray var. jepsonianus Barneby
Common Name:
 Jepson's milk-vetch
Family: Fabaceae
Element Code: PDFAB0F7E1
USDA Plants Symbol: ASRAJ
Synonyms/Other Names:

Ecology and Life History
Lifeform: annual herb
Blooming Period: Mar-Jun Mar-Jun
Elevation: 295-700 (970-2295)
General Habitats: Chaparral, Cismontane woodland, Valley and foothill grassland
Microhabitat: Serpentine (often)
Microhabitat Details:

Conservation Status
CA Rare Plant Rank: 1B.2
Global Rank: G4T3
State Rank:
 S3
State List: None
Fed List: None
Other Status: BLM_S; SB_UCSC
CRPR Changes:

Occurrence Data from the CNDDB
Total Occurrences: 54
Element Occurrence Ranks:
   Excellent (A) 9
   Good (B) 14
   Fair (C) 4
   Poor (D) 1
   None (X) 0
   Unknown (U) 26

Location
California Endemic:  True
California Counties and Islands: Name (Code)
Colusa (COL), Glenn (GLE), Lake (LAK), Napa (NAP), San Benito (SBT), Sonoma (SON), Tehama (TEH), Yolo (YOL)
Quads: Name (Quad Code)
Chrome (3912265), Cold Fork (4012226), Detert Reservoir (3812265), Gilmore Peak (3912235), Glascock Mtn. (3812283), Hall Ridge (3912276), Hough Springs (3912225), Idria (3612046), Jericho Valley (3812274), Knoxville (3812273), Leesville (3912224), Lower Lake (3812285), Lowrey (4012215), Middletown (3812275), Mount St. Helena (3812266), Newville (3912275), Paskenta (3912285), Salt Canyon (3912213), St. John Mtn. (3912246), Stonyford (3912245), Walter Springs (3812263), Whispering Pines (3812276), Wilbur Springs (3912214), Wilson Valley (3812284)

Threat List Data from the CNDDB

Threat List Total: 8
EOs with Threat Listed: Total EOs % of EOs
14 26 %
Non-native plant impacts 7 12%
Road/trail construction/maint. 7 12%
Foot traffic/trampling 3 5%
ORV activity 3 5%
Development 2 3%
Erosion/runoff 2 3%
Recreational use (non-ORV) 1 1%
Vandalism/dumping/litter 1 1%

Notes
Most occurrences small and widely scattered.
Threats:
Possibly threatened by road maintenance, vehicles, renewable energy development, and non-native plants.
Taxonomy:

Selected References

Aliso 4:137 (1958)
Memoirs of the New York Botanical Garden 13:1052 (1964)
Astragalus rattanii var. jepsonianus profile for potential Species of Conservation Concern evaluation (2018)
Systematic Botany 17(3):367-379 (1992) for distributional information
Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 27 January 2025].