CPC Plant Profile: Mason's Ceanothus
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Plant Profile

Mason's Ceanothus (Ceanothus masonii)

Photo Credit: © 2016 Aaron Arthur
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: N/A
  • Family: Rhamnaceae
  • State: CA
  • Nature Serve ID: 154612
  • Date Inducted in National Collection: 09/23/2021

Ceanothus masonii is a member of the buckthorn family and is endemic to the Point Reyes National Seashore in Marin County. As its common name suggests, the Bolinas Ceanothus is named after the coastal town Bolinas, CA where, here and along the seashore, you can spot C. masonii growing among the maritime chaparral on the coastal bluffs. Historically, C. masonii was thought to be a possible subspecies of another buckthorn species that also inhabits Point Reyes, Ceanothus gloriosus (the Point Reyes Ceanothus or Glory Mat) but has since been identified as a separate species. C. masonii is a spring bloomer that produces clusters of small, dark blue to purple flowers between March and April.

Participating Institutions
  • 09/01/2020
  • Orthodox Seed Banking

Based on an September 2020 extract of the California Plant Rescue Database, California Botanic Garden holds 1 accessions of Ceanothus masonii in orthodox seed collection. There are as many as 145 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.

  • 08/05/2020
  • Seed Collection

Based on an August 2020 extract of the California Plant Rescue Database, California Native Plant Society has collected 1 seed accessions of Ceanothus masonii from 1 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 4 maternal plants

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Taxon Ceanothus masonii
Authority McMinn
Family Rhamnaceae
CPC Number 856
ITIS 28487
Common Names Bolinas Ceanothus | Mason's Ceanothus
Associated Scientific Names Ceanothus gloriosus subsp. masonii
Distribution C. masonii is endemic to Marin County's Point Reyes National Seashore. 
State Rank
State State Rank
California S1

C. masonii is a shrub that grows on coastal bluffs with other maritime chaparral. 

Ecological Relationships

C. masonii has positive relationships with pollinating butterflies and bees. This species also attracts the prey of predatory insects. 

Common Name Name in Text Association Type Source InteractionID

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