Sonoma County is home to over 150 plant species or subspecies that are considered rare, threatened, or endangered. For a database that provides information on all of California’s rare plants (and is searchable by county and other factors), see the CNPS Inventory of Rare Plants.
The Inventory is linked to the California Natural Diversity Database (CNDDB), which is a repository for information about rare plant and animal occurrences throughout the state. Scientists, including many CNPS volunteers, submit data when they find a rare species in the field to contribute to our shared understanding of rare species distribution, biology, and threats. To view go to the CDFW or CNDDB websites but you need a subscription to access. For Sonoma County, go to the PRMD website and their arc-gis map for sensitive bio resources.
To submit data on a rare plant occurrence, see: https://wildlife.ca.gov/Data/CNDDB/Submitting-Data
Arctostaphylos bakeri ssp. sublaevis on barren (photo credit: Roger Raiche)
Sonoma County Endemic Plants
Many of Sonoma County’s rare species are also endemic here – they do not occur naturally anywhere else in the world. The excerpt below from A Flora of Sonoma County (Betty Guggolz, 1996, CNPS) explains why our area is so rich in species.
“Sonoma County is floristically rich, its vegetation diversity created, in part, by a broad range in altitude from sea level to 4000 feet, a wide variety of soils, a Mediterranean climate and an abundance of habitat types. Several of these habitats contain taxa that are endemic to Sonoma County, meaning that they do not occur naturally anywhere else in the world. Approximately 26% of Sonoma County’s 416 plant species, subspecies, and varieties listed as rare and endangered in the CNPS ‘Inventory’ are endemic to this county.”
“Approximately 42% of Sonoma County’s plant endemics are edaphic (soil) related, occurring in serpentine or on serpentine-related soils. The lack of nutrients, presence of heavy metals, sparse soil cover, and high erodibility discourage the growth of many species, leaving sufficient open space for plants that are serpentine-tolerant but unable to compete in heavily vegetated areas. How each serpentine-tolerant plant species adapts to the elements of serpentine, whether by screening out the toxics or selectively absorbing the needed nutrients, is one small part of a complex subject that needs more study to develop a better understanding of California’s serpentine flora. This need is further emphasized by the recent discoveries of three new serpentine endemic taxa in the county.”
Sonoma County Endemics
| Image | Name, Common Name & Family | Listing Status, Habitat & Season |
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Arctostaphylos bakeri ssp. sublaevis The Cedars manzanita Ericaceae family (Photo by Roger Raiche) |
Rare Plant Rank 1B.2 State Rare Serpentine ridges February–April |
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Arctostaphylos densiflora Vine Hill manzanita Ericaceae family (Photo by Sarah Gordon) |
Rare Plant Rank 1B.1 State Endangered Sandy soil, shale outcrops March–April |
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Blennosperma bakeri Sonoma sunshine Asteraceae family (Photo by Aaron Arthur) |
Rare Plant Rank 1B.1 State and Federally Endangered Vernal pools March–April |
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Calochortus raichei Cedars fairy lantern Liliaceae family (Photo by Aaron Arthur) |
Rare Plant Rank 1B.2 State Rare Serpentine areas May–June |
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Clarkia imbricata Vine Hill clarkia Onagraceae family (Photo by Sarah Gordon) |
Rare Plant Rank 1B.1 State and Federally Endangered Grassland June–July |
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Cordylanthus tenuis ssp.capillaris Pennell’s bird’s beak Orobanchaceae family (Photo by Aaron Arthur) |
Rare Plant Rank 1B.2 State Rare and Federally Endangered Serpentine chaparral July–September |
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Erigeron serpentinus Sepentine daisy Asteraceae family (Photo by Tony Morosco) |
Rare Plant Rank 1B.3 Serpentine soils, seeps June–July |
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Lilium pardalinum ssp. pitkinense Pitkin Marsh lily Liliaceae family (Photo by Kathi Dowdakin) |
Rare Plant Rank 1B.1 State and Federally Endangered Marshy habitats June–July |
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Plagiobothrys mollis var. vestitus (presumed extinct) Petaluma popcorn flower Boraginaceae family (Photo courtesy of Calscape) |
Rare Plant Rank 1A Salt marsh June–July |
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Sidalcea oregana ssp. valida Kenwood Marsh checkerbloom Malvaceae family (Photo by Sarah Gordon) |
Rare Plant Rank 1B.1 State and Federally Endangered Wet habitat June–July |
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Streptanthus glandulosus ssp. hoffmanii Hoffmann’s jewelflower Brassicaceae family (Photo by Roger Raiche) |
Rare Plant Rank 1B.3 Serpentine, rocky places March–May |