This is one of our most miss-understood native trees, the Horse chestnut (Aesculus californica). This picture highlights why the tree is so miss-understood. It goes dormant during summer and doesn't come out of dormancy until the rains return in fall. Right now the chestnuts are forming and will fall to the ground. There they will sprout and start a new tree. These trees are all over the place in the foothills. It is a common component of the chaparral. This is a very easy tree to grow.
Of course the problem is it looks like its dying during the summer, yet it is perfectly adapted to our summer droughts. Think about it, when there is no moisture to be had it goes dormant only to come out of dormancy when the rains return in fall. This is one reason we call fall the "second spring" around here.
Trees and plants like this that are so adapted to our climate will never become popular until we re look at what constitutes a "desirable" landscape here. California is a place where just about anything will grow with water. Why would someone moving here from different climates want a "dead" looking plants in their yard. Of course styles change when confronted with drought and a lack of water.
What we need here is a garden aesthetic that celebrates our climate. It's happening on a small scale with xeriscape and like climate gardens, but they are few and far between.While the Horse chestnut may not fit into the "look" most people are striving for, plants that are adapted to the dry summers will become more popular as we look for gardens that take less time to maintain.