It depends on how long it was allowed to go without water and how much heat it might have been exposed to (referring more to the pot and the root system therein). JM's in containers need pretty much constant attention in summer as the likelihood of them drying out, even in mild heat, is very high and can happen in just a few hours or a day. That combined with hot soil as a container might generate could be deadly.

But having said that, these trees can take more abuse than one would imagine :-) I recently experienced a near catastrophe in my own garden when the reconstruction and spray staining of a neighboring deck resulted in all the leaves of several containerized JM's being fully coated with deck stain!! While the plants were not at all happy and quickly produced dried and dropped leaves, they are responding with some new growth. I have also managed to overlook watering containerized maples from time to time and they eventually bounce back...........not always but very often :-)

Just keep it well hydrated but not overwatered and keep your fingers crossed. And be sure to pay careful and daily attention to any JM's grown in containers!!

Thanks. I moved the tree out of full sun and into a shaded location. I'm keeping my fingers crossed.

A lot of the branches are brown at the ends (a couple inches long to the tip). The branch tips are drooping. Any ideas? Do you think the whole tree will brown? Can the tree still recover? If the tree recovers should I prune the dead branches?

Stuart, it's hard to say how much recovery you can expect as we don't really know the extent of the potential damage. Sometimes it is not fully apparent for several months or until the next growing season!

Just keep it out of the direct sun/heat and water well as needed. You can prune off any dead wood at any time but I'd be inclined to leave everything as is for now and just wait and see how it goes.