Flame Eucalyptus, with a sturdy rounded form, is ablaze with orange-red flowers. Southern Magnolia displays its huge white flowers in most of the state. Lyonothamnus is the Catalina Ironwood. It has clusters of white flowers over a foot across. Cut them off when they turn brown in July.
Nerium oleander is one of the most widely used plants in California landscapes.
It grows along the central and south coasts, thrives in hot inland valleys, and is a standard in the desert. Oleanders on our highway medians get very little, if any, supplemental water in summer. Sadly, oleander is now being attacked by a new disease that is being spread by a new insect. The disease is oleander leaf scorch. The disease is so far confined to the southernmost counties - Riverside, Orange, San Diego.