Educate yourself with a book! "The Families of Native Trees in Southern California" by J. Zimmerman or P. Victor Peterson's classic book are starters. "Trees and Shrubs of California" by John Stuart/John Sawyer is a handy field guide. Research on internet although books travel with you easier. Combine trees and plants and learn with the kids!
In the deep south and mild winter areas the trees can found. we can identify the tree with their leaves and fruits in it. The age of the trees will be more and it will be small. you can see the wild flowers in the trees which gives a different look.