Taxon Report

Arctostaphylos osoensis Wells

Oso manzanita

Print Report

Taxon Summary

Arctostaphylos osoensis, commonly known as Oso manzanita, is a perennial evergreen shrub in the Ericaceae that is found only in California. It occurs within Chaparral, and Cismontane woodland, growing at elevations from 95 to 500 meters. Arctostaphylos osoensis is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

Classification


Scientific Name:	Arctostaphylos osoensis Wells
Common Name:	Oso manzanita
Family:	Ericaceae
Element Code:	PDERI042S0
USDA Plants Symbol:	AROS
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial evergreen shrub
Blooming Period: Feb-Mar	Feb-Mar
Elevation:	95-500 (310-1640)
General Habitats:	Chaparral, Cismontane woodland
Microhabitat:
Microhabitat Details:	dacite porphyry buttes

Conservation Status


CA Rare Plant Rank:	1B.2
Global Rank:	G1
State Rank:	S1
State List:	None
Fed List:	None
Other Status:	SB_UCSC
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	11
Element Occurrence Ranks:
Excellent (A)	1
Good (B)	0
Fair (C)	0
Poor (D)	0
None (X)	0
Unknown (U)	10

Location


California Endemic: True
California Counties and Islands: Name (Code)
San Luis Obispo (SLO)
Quads: Name (Quad Code)
Morro Bay South (3512037), San Luis Obispo (3512036)

Threat List Data from the CNDDB


Threat List Total:	0
EOs with Threat Listed:	Total EOs	% of EOs
	0	%

Notes



Known only from two occurrences in the mountains north of Los Osos Valley. Threatened by urbanization. See Four Seasons 9(2):45 (1992) for original description.
Threats:

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 3 March 2025].