My 5-year-old jacaranda has come back fairly well from this last winter's freeze in the Phoenix area, discussed above. As this tree had finally grown considerably taller than I am, I had lazily neglected to cover it during freeze warnings this year; in the spring, I wound up cutting it back to a couple of feet off the ground. It has produced several promising sturdy new branches. Now I'm concerned, though, about a number of vertical, superficial cracks that have opened up on the trunk. Would I be wise to spray on tree-wound dressing -- or are these cracks typical to the species and best left alone?