Updated list of plants highlights biological diversity and threats in our county

“Even more than the entire state of Montana.”

That’s how Jon Rebman, our curator of botany, describes the number of plants in San Diego County, which boasts more than any other county in the United States. Yep, we have more than some entire states do.

The reason? Our region is one of the most biodiverse and well-studied places in North America. According to the newest edition of Checklist of the Vascular Plants of San Diego County, our county is home to 2,879 documented plants—a number that has increased by more than 250 since the last edition came out just over 10 years ago.

But the checklist is never really complete. Even extremely well-studied places have new scientific discoveries. In just over a decade, botanists in San Diego have discovered 21 plants in the county that were recently described for science. Botanists have also marked an increase in the number of non-native plants, which is up to 32% of all plants in the county. That means that only about 68% of the plants on this list are actually native to our region.

While we have an incredible diversity of plants in our county, the increase of non-native plants can be problematic because they can:

• Outcompete native plants for resources like sunlight, water, and nutrients
• Disrupt food chains and ecosystem functions
• Alter habitat features like plant density and soil chemistry
• Hinder access to parks and choke hiking trails and waterways
• Contribute to the collapse of native insect populations
• Introduce uncommon allergies in humans

Having an updated list of what plants exist in our County helps us better understand our local plant diversity, how our environment is changing over time, and what needs to be protected. For example, the updated list includes 272 plants that are listed as rare, threatened, or endangered. Having this information helps us prioritize conservation efforts.

The new edition of the checklist can be purchased online or in-person at our Museum gift shop, Gold Leaf, for $14.99.

Posted by Paula Sternberg Rodríguez, Science Communications Manager.