Some common trees in Southern California include the white fir, Jeffrey pine, knobcone pine, lodgepole pine and the bristlecone pine. Broadleaf trees include the western sycamore, bigleaf maple, California black walnut, white alder, quaking aspen, black cottonwood, palo verde and several species of oak, including the California black oak. Evergreen broadleaf trees include species of live oak, the madrone, tanbark oak, fernleaf ironwood and California bay.
The bristlecone pine is one of the oldest living things on Earth. Some are 5,000 years old or older. They grow in poor, limestone soils at high altitudes in California. Because they're so exposed to the wind and the cold of the mountains and get little nutrition, the growth of these trees is very slow. Needles can persist on the trees for decades.
Palo verde is largely a desert tree, though the blue palo verde needs finer soil and more water than other types. Other kinds of palo verde tend to live longer than the blue type. This is probably because, as with the bristlecone pine, the environment is harsher. All types of palo verde have more or less green bark and a short and intense blossoming season in which they are covered in yellow flowers.