2024 April 21 Field Trip – Santa Rosa Plauteau

Santa Rosa Plateau
Field Trip
Sunday April 21
CNPS Members Only – Rain Cancels


Santa Rosa Plateau Ecological Reserve – vernal pool. Photo: Rachel Whitt

The Santa Rosa Plateau Ecological Preserve (SRPER), located at the Southern edge of the Santa Ana Mountains in western Riverside County, is one of our area’s most remarkable natural history and botanical sites. Varied soils, a basalt rock base, clay composition and a moderately level terrain have created a very special area for nature lovers.

Zach Principe, project director with The Nature Conservancy (TNC), will lead this amazing trip to this restricted-entry area of the SRPER, an area managed as a reserve by TNC, CDFW and Riverside County Parks. Zach refers us to Tom Chester’s website – Field Guide to the Santa Rosa Plateau, as a good information source for the field trip, including a list of plant species.  This field trip will include a post-fire recovery area, past chocolate lilies, and up to Mesa de Burro.  Field trip sign-ups are limited to CNPS members.


We will take a short hike through the 2019 Tenaja Fire burn scar on the Granite Loop Trail to observe the regrowth of the chaparral and a budding forb community before driving to the main area of the tour. We will drive through grasslands and oak savanna on our way to one of the seven plateaus of the area, Mesa de Burro, to observe the native Stipa pulchra grasslands and vernal pools. The vernal pools hold an assemblage of rare, beautiful and specialized plants, including two species of Downingia, Blennosperma nanum, Brodiaeas, Eryngium aristulatum var. parishii, Euphorbia spathulata, Isoetes howellii, Muilla maritima, Myosurus minimus, Orcuttia californica and Pilularia americana. We will walk 2-3 miles over relatively flat, but uneven ground through very healthy and diverse grasslands and discuss the ecology of the area and the plants present.

Vehicles with high clearance and 4-wheel drive are required to drive to Mesa de Burro. We will meet and carpool in the 4 WD vehicles from the SRPER Visitor Center.  If we do not have enough 4×4 vehicles, we will hike to the location (as we did in 2022).

An alternative hike could also occur due to unfavorable weather and dangerous road conditions. If we get significant rain the week before the event, we won’t be able to go up to Burro Mesa; and instead, will visit the Vernal Pools on Colorado Mesa.



Click Here for Waiver Sign – Registration. 
This trip is limited to the first 20 CNPS members who register-waiversign. Rain Cancels.



Meet:  9:00AM at the SRPER Visitor’s Center, 39400 Clinton Keith Rd, Murrieta, CA 92562.
Duration:  4-5 hours, depending on the group.
Bring:  Trail boots/shoes, hat, sunscreen, camera, binoculars, water and lunch.
Physical Difficulty:  Moderate.
Facilities:  Water and restrooms available at the Visitor Center.
Plant Intensity:  High.
Leader, Local Expert:  Zach Principe, The Nature Conservancy.
Leader, CNPS-OC:  Rachel Whitt, socaljaguar6@gmail.com.

  1. Before arriving, please clean out boots, pant cuffs, pockets, bags, etc., of all seeds to prevent spreading of invasive weeds.
  2. We will be spraying car tires and boots on arrival with hydrogen peroxide to prevent the spread of rabbit hemorrhagic disease and soil and water borne pathogens in the Phytophthora genus.


Oak at Santa Rosa Plateau. Photo: B. Jenkins