The Santa Rosa Plateau is an upland plateau and southeastern extension of the Santa Ana Mountains in Riverside County, southern California. It is bounded by the rapidly urbanizing Inland Empire cities of Murrieta and Temecula to the northeast and southeast, respectively. The Santa Rosa Plateau Ecological Reserve preserves approximately of the plateau, and includes the Moreno and Machado Adobes, Riverside County’s oldest standing structures, and other buildings from the 19th century Mexican land grant Rancho Santa Rosa. Habitats The Santa Rosa Plateau is home to several native plant communities and habitats, including purple needlegrass prairie (Nassella pulchra), California oak woodland (Engelmann Oaks—Quercus engelmannii), montane chaparral, coastal sage scrub, and vernal pools, which are increasingly rare in urbanized Southern California. The Engelmann oak was once widespread throughout the western U.S. Now the farthest north they are found is Pasadena. The Reserve has the only protected, reproducing Engelmanns in the states. A vernal pool is a shallow depression in the soil which fills up with water during spring rains. Fairy shrimp and other minute crustaceans hatch during this time and lay eggs. These eggs remain dormant during the dry months until the next rainy season allows them to hatch. (6) Santa Rosa Plateau Ecological Reserve The Santa Rosa Plateau Ecological Reserve was assembled in several stages; two parcels, comprising , were purchased by The Nature Conservancy in 1984. The intervening parcels were purchased in the 1990s by the State of California, the Riverside County Regional Park and Open-Space District, and the Metropolitan Water District of Southern California. Although the parcels remain under the ownership of separate agencies, they are managed cooperatively, with biological resource management, which includes prescribed fire and habitat restoration programs managed by the Nature Conservancy, and visitor management. This includes operation of a visitor center and a trail system, managed by the Riverside County Parks (RivCo Parks). A non-profit organization, the Santa Rosa Plateau Nature Education Foundation, provides funding for field trips to the Reserve for all third-graders in the area. Flowers The Reserve is home to many species of flowers. In one month, March 1998, 50 different wildflowers were reported in bloom. The best time to view the flowers is in the spring and the best trail for flowers at this time is the Vernal Pool Trail. The one flower people come specifically to the Reserve to see is the Chocolate Lily. It is most often seen in