Desert Museum Palo verde Dying
I live in La Mesa, Ca. It is inland a little and pretty hot. My soil is fast-draining sandy loam. I have a Palo verde x 'Desert Museum' in the ground for 3 years. It is in mostly full sun and has grown a lot. The caliper is 3". It has never been without leaves until now. It bloomed for a long time this spring and summer and about a month ago I noticed it had dropped all its leaves. Someone suggested I water it deeply and slowly as it has deep roots, so I did. Now, not only are the leaves gone, but some of the small branches are browning as well. I don't want to lose this tree. I thought maybe it had gophers eating the roots, but the tree seems really stable. What is wrong?