Jeanie, try to plant that plum where it is out of the wind. It's a beautiful tree, but hot wind will tatter the leaves.
I'm in Kansas, where we have lots of hot wind. .
but my middle daughter lives in Phoenix and I do remember how hot it is there in September! If the tree is in a box, how big a hole do you have to dig? Do you have someone to dig or are you using heavy equipment?
You might even consider putting a large patio umbrella next to the tree for a few days after planting just to help it out. Spray the leaves a tad to cool it off on hotter days for the first few weeks...but don't drown the tree.
My purple leafed plums will absolutely wilt on hot days, but it's not lack of water. It's just heat stress, so don't assume it's thirst when leaves droop.
And,
to ATP!
