Classic Mediterranean trees are all waterwise: olive, acacia, crape myrtle, sweet bay, catalpa and Italian cypress.  Low-water California classics fill out the list: goldenrain tree (great for parkways) won’t lift walls or sidewalks) eucalyptus, ginkgo, arbutus, cedar, redbud, red-leaf plum, Catalina cherry, Chinese pistache, oak, black locust, honey locust andMelaleuca.  Well-established citrus trees can be quite drought-tolerant but require regular water to establish. Don’t remove old citrus trees, as they will tolerate dry soil.