The annual wildflower bouquets are out on the normally sparse serpentine ridges in the Peninsula Watershed.
The 36-square-mile watershed has been home to the Peninsula segment of SFPUC’s regional water system since the mid-19th century. The land with its reservoirs, streams and unspoiled surrounding ridges has been carefully protected to safeguard the quality of the water supply. The relatively secluded area also harbors a rich diversity of native coastal habitats that support an abundance of plant and animal life—including the highest concentration of rare, threatened and endangered species in the Bay Area.
Serpentine is California’s state rock—a gray-greenish rock originating from the earth’s mantle (and closely associated with earthquake fault lines). Its thin covering of serpentine soil is high in magnesium and iron, but low in plant-nutritious calcium, aluminum, and clay. So most of the year, what plants can survive there are limited to stubby low-growing native grasses and small herb-like plants. But, come spring, the ridges are covered with native wildflowers—some rare—that thrive for a few colorful weeks in the harsh conditions so unfavorable to their more common or non-native competitors.
In all, the Peninsula Watershed has over 800 species of plants and trees, 165 species of birds, 50 mammal species and 30 species of reptiles and amphibians. It is a California State Fish and Game Refuge.
Members of the public can experience the watershed through the Fifield-Cahill Ridge Trail Program, which offers a variety of guided hikes and bike rides on selected Wednesdays, Saturdays and Sundays throughout the year.