Almost 7,000 flowering plants, gymnosperms (pines and other cone-bearers), ferns and fern allies are native to California, more than are found in the entire northeastern United States and adjacent Canada, an area 10 times larger. The state's mountain ranges and deserts and its unusual summer-dry climate set the stage for development of a complex flora.
About one-third of the California flora is endemic--plants that are restricted to a particular locality or habitat within the state. In an area botanists define as the California Floristic Province, that part of that state west of the Sierra Nevada-Cascades axis and including parts of southern Oregon and northern Baja California, the degree of endemism rises to 47.7%, which is unmatched in continental flora.
A number of rare and unusual plants are threatened with extinction in California because of development and other disruptions of their habitats. The California Native Plant Society, in its 1984 inventory, listed 21.8% of the state's vascular plants as rare or endangered. The California Nature Conservancy, in a recent study, reported that 118 native plant species or subspecies in the state are officially listed as threatened or endangered by the state or federal governments, and another 487 have the potential to qualify.