''Ceanothus sonomensis'', with the common name Sonoma ceanothus, is a rare species of shrub in the family Rhamnaceae. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to northern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

Description

The ''Ceanothus sonomensis'' shrub is erect in form, approaching a maximum height of one meter. The flat evergreen leaves are oppositely arranged, each oval to rounded in shape with spiny teeth along the edges. They are shiny green on top, paler and fuzzy on the undersides. The

inflorescence An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...

is a small cluster of blue or lavender flowers, and the fruit is a ridged, horned capsule about half a centimeter long.

Distribution

''Ceanothus sonomensis'' is known only from the

Hood Mountain Mount Hood, also known as Hood Mountain is a mountain near the southeastern edge of Santa Rosa, California at the northeast of the Sonoma Valley and attains a height of . The original name was Mount Wilikos, an Indian name meaning "willows." ...

Range. Most of its 10 or so occurrences are located in

Sonoma County Sonoma County () is a county located in the U.S. state of California. As of the 2020 United States Census, its population was 488,863. Its county seat and largest city is Santa Rosa. It is to the north of Marin County and the south of Mendocino ...

, and one remains in

Napa County Napa County () is a county north of San Pablo Bay located in the northern portion of the U.S. state of California. As of the 2020 census, the population was 138,019. The county seat is the City of Napa. Napa County was one of the original c ...

.California Native Plants Society Rare Plant Profile
/ref> ''Ceanothus sonomensis'' is a member of the chaparral

plant community A plant community is a collection or association of plant species within a designated geographical unit, which forms a relatively uniform patch, distinguishable from neighboring patches of different vegetation types. The components of each plant ...

in the

California montane chaparral and woodlands The California montane chaparral and woodlands is an ecoregion defined by the World Wildlife Fund, spanning of mountains in the Transverse Ranges, Peninsular Ranges, and Coast Ranges of southern and central California. The ecoregion is part of ...

sub-

ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of ...

References

External links

Jepson Manual Treatment - ''Ceanothus sonomensis''USDA Plants Profile: Ceanothus sonomensis''Ceanothus sonomensis'' - Photo gallery
sonomensis Endemic flora of California Natural history of the California chaparral and woodlands Natural history of the California Coast Ranges Natural history of Sonoma County, California Plants described in 1939 Taxa named by John Thomas Howell {{Rhamnaceae-stub