The Nacimiento watershed includes several different types of California oak woodland communities, including blue oak, coast live oak, and valley oak mixed with foothill pine, manzanita and chaparral. Montane hardwood-conifer forests dominated by Coulter pine occur at higher elevations, primarily in the headwaters. Valley floors consist of a mix of native bunchgrass and needlegrass as well as non-native annual grasses seeded for grazing. Because most streams in the watershed are seasonal, there are only small areas of riparian and wetland habitat.