Each spring a flush of green grasses covers the rolling hills and bluffs above the sea, and within a few weeks thousands of wildflowers burst forth in brilliant colors. By midsummer the grasses set seed and the hill change back to their green and golden slumber. This is the coastal prairie community, which extends intermittently south from Eureka to Point Reyes and between San Francisco and Monterey.
Until late in the last century the coastal prairie was almost entirely composed of native perennial grasses. These relatively slow-growing grasses have deep root systems and creeping stems that help to ensure their long-term survival; some individual plants are known to be more than 100 years old. Early European settlers found the naturally treeless coastal grasslands ideal for agriculture and ranching. As grazing operations expanded, fast-growing, non-native annual grasses were gradually introduced and these began to outcompete the slow-growing, native perennials. Some introductions were accidental and others were intentional. Annual grasses live only a single growing season but good seed dispersal ensures their return year after year. As a result, few intact native grassland communities remain today.
Representative native grasses include species of bentgrass, Agrostis; hairgrass, Deschampsia; reedgrass, Calamagrostis; and oatgrass, Danathonia. At least four species of bentgrass are endemic, whereas others are introductions from Australia and Europe. Hairgrass provides excellent forage and can withstand close grazing without destruction of its delicate root system, whereas reedgrass is important in the prevention of erosion. Commonly encountered non-native grasses include wild oat, Avena spp., and bromegrass, Bromus spp.