Taxon Report

Ceanothus masonii McMinn

Mason's ceanothus

Print Report

Taxon Summary

Ceanothus masonii, commonly known as Mason's ceanothus, is a perennial evergreen shrub in the Rhamnaceae that is found only in California. It occurs within Chaparral (openings, rocky, and serpentinite), growing at elevations from 230 to 500 meters. Ceanothus masonii is ranked 1B.2, Plants Rare, Threatened or Endangered in California and Elsewhere; Moderately threatened in California.

Classification


Scientific Name:	Ceanothus masonii McMinn
Common Name:	Mason's ceanothus
Family:	Rhamnaceae
Element Code:	PDRHA04200
USDA Plants Symbol:	CEMA3
Synonyms/Other Names:

Ecology and Life History


Lifeform:	perennial evergreen shrub
Blooming Period: Mar-Apr	Mar-Apr
Elevation:	230-500 (755-1640)
General Habitats:	Chaparral
Microhabitat:
Microhabitat Details:

Conservation Status


CA Rare Plant Rank:	1B.2
Global Rank:	G1
State Rank:	S1
State List:	CR
Fed List:	None
Other Status:	SB_CalBG/RSABG; SB_USDA
CRPR Changes:

Occurrence Data from the CNDDB


Total Occurrences:	8
Element Occurrence Ranks:
Excellent (A)	1
Good (B)	2
Fair (C)	1
Poor (D)	0
None (X)	0
Unknown (U)	4

Location


California Endemic: True
California Counties and Islands: Name (Code)
Marin (MRN)
Quads: Name (Quad Code)
Bolinas (3712286), Petaluma (3812226), Point Reyes NE (3812227)

Threat List Data from the CNDDB


Threat List Total:	4
EOs with Threat Listed:	Total EOs	% of EOs
	5	63 %
Grazing	2	25%
Improper burning regime	2	25%
Road/trail construction/maint.	2	25%
Other	1	12%

Notes



Known from approximately five occurrences. Threatened by fire suppression. May be a variety of C. gloriosus; needs further study. See Madroño 6(5):171-173 (1942) 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 16 April 2025].