Taxon Report

Ceanothus divergens Parry

Calistoga ceanothus

Print Report

Taxon Summary

Ceanothus divergens, commonly known as Calistoga ceanothus, is a perennial evergreen shrub in the Rhamnaceae that is found only in California. It occurs within Chaparral (rocky, serpentinite, and volcanic), growing at elevations from 170 to 950 meters. Ceanothus divergens is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

Classification


Scientific Name:	Ceanothus divergens Parry
Common Name:	Calistoga ceanothus
Family:	Rhamnaceae
Element Code:	PDRHA04240
USDA Plants Symbol:	CEDI
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial evergreen shrub
Blooming Period: Feb-Apr	Feb-Apr
Elevation:	170-950 (560-3115)
General Habitats:	Chaparral
Microhabitat:
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.2
Global Rank:	G2
State Rank:	S2
State List:	None
Fed List:	None
Other Status:	BLM_S; SB_UCSC
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	26
Element Occurrence Ranks:
Excellent (A)	2
Good (B)	5
Fair (C)	3
Poor (D)	2
None (X)	0
Unknown (U)	14

Location


California Endemic: True
California Counties and Islands: Name (Code)
Lake (LAK), Napa (NAP), Sonoma (SON)
Quads: Name (Quad Code)
Calistoga (3812255), Detert Reservoir (3812265), Kenwood (3812245), Mark West Springs (3812256), Mount St. Helena (3812266), Rutherford (3812244), Santa Rosa (3812246), St. Helena (3812254), The Geysers (3812277), Whispering Pines (3812276)

Threat List Data from the CNDDB


Threat List Total:	8
EOs with Threat Listed:	Total EOs	% of EOs
	11	42 %
Improper burning regime	3	11%
Agriculture	3	11%
Development	3	11%
Foot traffic/trampling	2	7%
Other	2	7%
Road/trail construction/maint.	2	7%
Wood cutting or brush clearing	1	3%
Erosion/runoff	1	3%

Notes



Threatened by habitat alteration and development in The Geysers geothermal area and by fire suppression. Closely related to C. purpureus.
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 24 March 2025].