The following excerpt was taken from the Native Plant Society Website. Visit their website at http://www.cnps.org
What is a native plant?
Native plants are in California are those that grew here prior to European contact. California's native plants evolved over a very long period, and are the plants which the first Californians knew and depended on for their livelihood. Our native plants have co-evolved with animals, fungi and microbes, to form a complex network of relationships. Native plants are the foundation of our native ecosystems and natural communities.
How do we know which plants are native?
Specimens, seeds and drawings of new world plants were taken to Europe by early explorers over many years. By comparing fossil records with modern plants, researchers can confirm their theories as to which plants are native to California. While there is general agreement among plant scientists on which California plants are native, there is still some debates. An example is the Sea Fig, or Common Coast Ice Plant, (Carpobrotus chilensis) once thought to be native, but now widely regarded as an alien. Other questions involve the original distribution of some plants, such as the northern range limit of the Coast Bush Lupine (Lupinus arboreus).
Why are native plants important?
Native plants have evolved over the years. They provide essential environmental tasks, such as manufacturing oxygen and filtering impurities from our water. These plants also do the best job of providing food and shelter for native wild animals. Different animal populations require maximum diversity of plants. Biological diversity is vital to humans, because ultimately, we all live off the land, whether we admit it or not. Native plants continue to play a crucial role in the development of new foods, medicines and industrial products. Commercial sunflower seeds were developed using our Common Sunflower (Helianthus annuus). The Pacific Yew (Taxus brevifolia) yields Taxol, an anti-cancer drug. Monterey Pine (Pinus radiata) is an important timber crop throughout much of the world.Native plants are also a major element in the natural beauty for which California is famous.