Taxon Report

Ambrosia monogyra Torr. & Gray

singlewhorl burrobrush

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Taxon Summary

Ambrosia monogyra, commonly known as singlewhorl burrobrush, is a perennial shrub in the Asteraceae that is found in California and elsewhere. It occurs within Chaparral, and Sonoran desert scrub, growing at elevations from 10 to 500 meters. Ambrosia monogyra is ranked 2B.2, Plants Rare, Threatened, or Endangered in California, But More Common Elsewhere; Moderately threatened in California.

Classification


Scientific Name:	Ambrosia monogyra Torr. & Gray
Common Name:	singlewhorl burrobrush
Family:	Asteraceae
Element Code:	PDAST50010
USDA Plants Symbol:
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial shrub
Blooming Period: Aug-Nov	Aug-Nov
Elevation:	10-500 (35-1640)
General Habitats:	Chaparral, Sonoran desert scrub
Microhabitat:	Sandy
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	2B.2
Global Rank:	G5
State Rank:	S2
State List:	None
Fed List:	None
Other Status:	SB_CRES
CRPR Changes:	changed from 2.2 to 2B.2 on 2013-06-12 added to 2.2 on 2007-02-21

Occurrence Data from the CNDDB


Total Occurrences:	30
Element Occurrence Ranks:
Excellent (A)	0
Good (B)	2
Fair (C)	4
Poor (D)	0
None (X)	0
Unknown (U)	24

Location


California Endemic: False
California Counties and Islands: Name (Code)
Riverside (RIV), San Bernardino (SBD), San Diego (SDG)
Quads: Name (Quad Code)
Cuyamaca Peak (3211685), Descanso (3211675), Devore (3411724), Dulzura (3211667), Imperial Beach (3211751), Jamul Mountains (3211668), La Jolla (3211772), La Mesa (3211771), Mecca (3311651), National City (3211761), Otay Mesa (3211658), Otay Mountain (3211657), Palm Springs (3311675)

Threat List Data from the CNDDB


Threat List Total:	4
EOs with Threat Listed:	Total EOs	% of EOs
	6	20 %
Non-native plant impacts	3	10%
Other	2	6%
Road/trail construction/maint.	2	6%
Grazing	1	3%

Notes



Possibly threatened by trail maintenance and non-native plants. See Hymenoclea monogyra in TJM (1993). See Madrono 49: 143 (2002) for taxonomic treatment.
Threats:

Taxonomy:

Selected References

Proposed Addition to CRPR 2B.2 (2007)

Citation California Native Plant Society, Rare Plant Program. 2025. Rare Plant Inventory (online edition, v9.5.1). Website https://www.rareplants.cnps.org [accessed 23 February 2025].