Taxon Report

Astragalus atratus Wats. var. mensanus Jones

Darwin Mesa milk-vetch

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Taxon Summary

Astragalus atratus var. mensanus, commonly known as Darwin Mesa milk-vetch, is a perennial herb in the Fabaceae that is found only in California. It occurs within Great Basin scrub, Joshua tree "woodland", and Pinyon and juniper woodland, growing at elevations from 1340 to 2315 meters. Astragalus atratus var. mensanus is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.

Classification


Scientific Name:	Astragalus atratus Wats. var. mensanus Jones
Common Name:	Darwin Mesa milk-vetch
Family:	Fabaceae
Element Code:	PDFAB0F0Z3
USDA Plants Symbol:	ASATM
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial herb
Blooming Period: Apr-Jun	Apr-Jun
Elevation:	1340-2315 (4395-7595)
General Habitats:	Great Basin scrub, Joshua tree "woodland", Pinyon and juniper woodland
Microhabitat:	Clay, Gravelly, Volcanic
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.1
Global Rank:	G4G5T2
State Rank:	S2
State List:	None
Fed List:	None
Other Status:	BLM_S
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	11
Element Occurrence Ranks:
Excellent (A)	0
Good (B)	0
Fair (C)	0
Poor (D)	0
None (X)	0
Unknown (U)	11

Location


California Endemic: True
California Counties and Islands: Name (Code)
Inyo (INY)
Quads: Name (Quad Code)
Cactus Peak (3611717)?, Coso Peak (3611726), Hanging Rock Canyon (3711726), Homewood Canyon (3511784), Jackass Canyon (3611755), Last Chance Mtn. (3711736), Mountain Springs Canyon (3511785), Upper Centennial Flat (3611727)

Threat List Data from the CNDDB


Threat List Total:	1
EOs with Threat Listed:	Total EOs	% of EOs
	2	18 %
Grazing	2	18%

Notes



See Memoirs of the New York Botanical Garden 13:473 (1964) for taxonomic treatment.
Threats:
Threatened by grazing.
Taxonomy:

Selected References

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 1 November 2025].