Taxon Report

Ceanothus thyrsiflorus Eschsch. var. obispoensis D. O. Burge

San Luis Obispo ceanothus

Print Report


Taxon Summary

Ceanothus thyrsiflorus var. obispoensis, commonly known as San Luis Obispo ceanothus, is a perennial shrub in the Rhamnaceae that is found only in California. It occurs within Chaparral, and Cismontane woodland, growing at elevations from 140 to 225 meters. Ceanothus thyrsiflorus var. obispoensis is ranked 1B.1, Plants Rare, Threatened or Endangered in California and Elsewhere; Seriously threatened in California.

  Classification
Scientific Name:
 Ceanothus thyrsiflorus Eschsch. var. obispoensis D. O. Burge
Common Name:
 San Luis Obispo ceanothus
Family: Rhamnaceae
Element Code: PDRHA04461
USDA Plants Symbol:
Synonyms/Other Names:

Ecology and Life History
Lifeform: perennial shrub
Blooming Period: Jun Jun
Elevation: 140-225 (460-740)
General Habitats: Chaparral, Cismontane woodland
Microhabitat:
Microhabitat Details: Dacite

Conservation Status
CA Rare Plant Rank: 1B.1
Global Rank: G5T1
State Rank:
 S1
State List: None
Fed List: None
Other Status: SB_UCSC
CRPR Changes:
  • added to 1B.1 on 2019-01-30

Occurrence Data from the CNDDB
Total Occurrences: 3
Element Occurrence Ranks:
   Excellent (A) 0
   Good (B) 0
   Fair (C) 0
   Poor (D) 0
   None (X) 0
   Unknown (U) 3

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

Threat List Data from the CNDDB

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

 

Notes
Similar to C. thyrsiflorus var. griseus; differentiated by dense, wavy, matted hairs on abaxial surfaces of young leaves and twigs, often forming a tomentum that obscures tertiary leaf venation.
Threats:
Potentially threatened by urbanization.
Taxonomy:

Selected References

Proposed Addition to CRPR 1B.1 G5T1/ S1 (2019)
Systematic Botany 42(3):529-542 (2017)
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].