Ceanothus decornutus (Nicasio ceanothus)

by Doreen Smith

Never think that Marin County has been botanized so thoroughly that there are no new native species that can be discovered here. Discoveries have been made by several people, who, exploring the wildlands, paid careful attention to unusual plants. To know something is unusual takes experience; first you have to know, by sight, most of the species usually found in Marin to recognize any exceptions.

Some years ago, a large population of Ceanothus was discovered on the hills southwest of Nicasio Reservoir, on the McIsaac Ranch. Several taxonomists and other experts visited the site (a large serpentine Smithrock outcrop) and gave their opinions as to what it should be called. Most thought the shrubs were some form of Ceanothus jepsonii, but the flowers differ from that more common serpentine soil-endemic shrub in several respects.

Nicasio ceanothus consistently has five-petalled flowers versus the six petals of C. jepsonii, and the flowers vary in color from shrub to shrub. They can be blue-purple, pink, or white. In describing it for publication, V. Thomas Parker of San Francisco State University zeroed in on the distinctive fruit shape, which is “hornless,” so naming it Ceanothus decornutus in Latin. The land is now part of the GGNRA, but access is only by permission with a NPS botanist as the leader.

Photos by Vernon Smith

Ceanothus decornutus (Nicasio Ceanothus)

Ceanothus decornutus (Nicasio Ceanothus) Blue form

Ceanothus decornutus (Nicasio Ceanothus) Fruits