The living collection of the Regional Parks Botanic Garden is composed of plant species native to the state of California and to the California Floristic Province (CFP). The CFP extends into southwesternmost Oregon and into northwesternmost Baja California, Mexico, and can be roughly characterized as the region that has a Mediterranean-type climate. This climate type is notable for its cool, moist winters and warm, dry summers. Mediterranean climates are globally rare (about 2% of the world's land mass) and are noted global biodiversity hotspots.

Plant life in Mediterranean-type climates has a number of distinctive adaptations to living in a summer-dry environment including: small, leathery, evergreen leaves that are often covered with hairs and aromatic sticky material. Woodlands, shrublands, and grasslands are characteristic vegetation types that are found in these climates. True forests with closed canopies are rare. Annual species (where the plant avoids the dry summer months as seeds) and geophytes (bulbs, corms, rhizomes, tubers, etc.) are also commonly found in Mediterranean-type climates, as these water and nutrient storage organs remain hidden and insulated underground.