Several months ago, I planted three cherry trees, one in the front garden, one in the back and one in a container in the house. The one in the front has really struggled, whereas, predictably, the one I kept inside has flourished. Four days ago, I dug up the one in the front garden and swapped it with the one I grew inside. I notice today on the one I moved outside that some of the leaves have gone pale, almost white, and flimsy. What does this mean? I've watered it regularly, every three days or so, but maybe not in great enough volume. We have had some rain, but also some very hot weather in the last 48 hours. I live in the UK.
As already mentioned, you needed to harden it off before transferring outside, especially this year in the UK when we've had the equivalent of winter temperatures up until the last couple of days. It's still cold at night as well, so its transition shock. You do need to make sure the tree gets a good water supply (this applies to any newly planted tree, especially if planted any time other than late autumn/winter) at least once a week of a good few gallons. You'll probably find the leaves fall off, but new ones should appear once the plant has acclimatized.
UPDATE: Giving it a good soak every 5 or 6 days, maybe by leaving the hose trickling at the base for an hour or so, or with several gallons of water from a can, is much better than frequent, lesser waterings. You want the plant to put out its own water seeking roots deep into the ground, and a small amount of water 3 or 4 times a week from the owner means the plant tends to form these nearer the surface.