Rare, Unusual, and Significant Plants of Alameda and Contra Costa Counties

The East Bay is the great melting pot of California’s diverse vegetation with the convergence of plants from the Pacific coast, the interior Great Valley, the cooler mesic north, and the warmer drier south. Many native plants here occur only in limited or threatened habitats or in small isolated populations, and 182 plant species currently meet their range limits in the two counties of the East Bay.

With this wealth of plant diversity, it is not surprising that the East Bay is home to so many rare and vulnerable plants, including many that are rare statewide and even more that are locally rare in our two-county area. Approximately 100 of our native plants have only one known current population in Alameda and Contra Costa counties.

The CNPS East Bay Chapter has been tracking and monitoring rare and locally rare (also known as “unusual”) species for over 30 years in an effort to protect and ensure the health and continuance of these important but vulnerable plants and has long maintained a database of the results. The following webpages draw on that database to provide information on rare and unusual plant populations in easy-to-access and clearly defined lists, with links to the database and other resources for more detailed or extensive data. The lists provide pre-searched and pre-sorted data that is most frequently sought after by agencies, organizations, private companies, and researchers, as well as by wildflower and plant enthusiasts.