To grow that fast, the tree would have to had far more water than it gets in its native desert environment. Palo verde wood is not very ligneous so it is susceptible to rotting if over watered. To bad, they are beautiful trees.

It sounds like your tree may have had what's called included bark. It is common in branch attachments that are narrow or less than 45 degrees. Some tree varieties are prone to these weak attachments. Instead of the bark being pushed up in the branch angle, it rolls in. Instead of a wood-to-wood connection in the branch union, it is replaced by bark-to-bark and the strength is compromised. Strong attachments are characterized by a branch bark ridge, or area of tissue that is 'pushed' up in between the branches or branch and trunk.

For now you can trim away the torn wood and leave the wound as clean as possible. Do not use sealants of any kind as these trap pathogens against the tissue in a dark, damp environment - perfect for decay. You can spray the wound with a 10 percent bleach solution if you like.

Your tree may recover but my fear is that the strength of the remaining trunk had been weakened. When a branch tears in this manner it usually takes a portion of the branch or trunk next to it, sometimes leaving only one-half of the former volume.

Should you decide to replace the tree, look for one with strong branch unions. If you select a native tree (mesquite, palo verde, acacia, ironwood, etc.,) be sure to water appropriately for the species. Remember that trees that grow rapidly typically have weaker wood than those that grow slowly (oak vs. mesquite for example).

Here's a link to information on watering landscape plants. On page 14 is a guide for newly installed plants.

Let me know if you have any questions.

Good luck.

AZtreelvr
Certified Arborist

Here is a link that might be useful: Landscape Watering by the Numbers