The Mexicali or Mex Buttercup (Ranunculus macropetalus) is a rare, endemic plant species found only in the Salton Sea watershed of California. It is a member of the buttercup family and is characterized by its showy yellow flowers that bloom between February and April. The plant grows in ephemeral pools and wetlands, which are typically found in the Imperial Valley, Coachella Valley, and surrounding areas. Due to its limited distribution and habitat loss, the Mexicali Buttercup has been listed as a threatened species by the US Fish and Wildlife Service.

Visiting the Salton Sea watershed to see the Mexicali Buttercup can be a unique and rewarding experience. The area is known for its scenic beauty, diverse wildlife, and rich cultural heritage. In addition to the rare plant species, visitors can observe numerous migratory bird species such as the American white pelican, great egret, and snowy plover. The Salton Sea National Wildlife Refuge and Sonny Bono Salton Sea National Wildlife Refuge are popular destinations for birdwatching and wildlife observation. The region is also rich in history and offers opportunities to explore the local towns, museums, and galleries that showcase the area's unique cultural and artistic heritage.