Thirty per cent of the state's native plant species are found only in California. These are called endemics. Common endemic plants include many species of manzanita and monkeyflower. A striking feature of the California flora is the mix of evolutionary "young" and "old" species. Tree species such as coast redwood, which date back millions of years, provide a glimpse into the primordial past, whereas species of tarweed, are of recent origin, perhaps only a few thousand years old.
Botanists divide the plant kingdom into several major morphological groups. Flowering plants are the largest of these, in terms of the total number of species they contribute to the plant kingdom, but the other, smaller groups are equally important. These include conifers, ferns and their allies, mosses, and algae. All of these groups are distinguished on the basis of three general characteristics: type of vascular tissue differentiation--presence or absence of special vascular cells called xylem and phloem that are essential for transport of water and nutrients within the plant; their overall morphological organization--presence or absence of roots, stems, and leaves; and their reproductive organs--presence or absence of cones, flowers, or other structures.
Plants are also classified by where they grow. The number and kinds of species found in a particular place are the result of complex interactions between different species, and between the plants and the physical environment. Such ecological assemblages of species are called plant communities. Some communities, such as the coastal strand, are relatively simple, consisting of a few plants adapted to a highly specialized environment. In contrast, grasslands and forests are extremely complex; hundreds of species coexist through a dynamic ecological balance. Ecologists recognize as many as 80 different plant communities constituting what is known as the California Floristic Province. Eleven of these communities, of which five are tree communities, are represented along the California coast.