SOIL. Depending on where you live, your soil can be heavy clay, alkaline (which plants such as camellias don't like), or salty (especially in the desert). To lighten clay soils, add amendments such as compost. To acidify alkaline soils, mix in peat or acid fertilizer periodically. To leach (wash) salts from the salty soils, water plants' root zones slowly and deeply at least once a year.
WIND. Warm winds that sweep from east to west in late summer can dry out foliage and blow down young trees. Properly stake newly planted trees; prune dead or weak branches from established ones. Deeply irrigate plants.
WATER. Dry summers, recurring drought, and a limited water supply are realities in California. Choose plants that adapt well to aridity, and group them by water needs.
PRIVACY. It's an increasingly valuable commodity in California, especially in urban areas where houses are close together and lots are small. To block unwanted views, use leafy screens of closely spaced, fast-growing shrubs such as purple hop bush.
FIRE. In fire-prone areas (Malibu, Bel Air, Santa Barbara, or the hills behind San Bernardino, Laguna Beach, or Oakland, for example), avoid growing highly flammable plants such as junipers, manzanita, or pines. Create an irrigated greenbelt around your house, and clear out any branches that overhang your roof.