Answer: Fall is a great time to plant, it allows the roots time to grow while the soil remains warm without the stress of the top growth trying to grow simultaneously as happens in the spring. Usually leaf loss at the center and base first would indicate overwatering and/or possibly planting too deeply. The tree should be set at the same depth as it grew in the container or slightly higher so that the flare at the base of the trunk is not under the soil. If you can't see the flare it is too deep and needs to be reset.
Your goal in watering is to keep the soil slightly moist like a wrung out sponge, not sopping wet or saturated. You only need to apply supplemental water if the soil is drying out. Very often the initial thorough watering at planting time to settle air pockets is sufficient for quite some time, especially if the plant is mulched as it should be.
To know if you need to water, push aside the mulch and dig into the soil with your finger. If it is still damp, do not water yet. When you water, apply it slowly and thoroughly so it soaks down deep and encourages deep rooting. After watering, wait a few hours and then dig down to see how far it actually soaked in, sometimes it is surprising. It is better to water less often but deeply than to water lightly every day.
Finally, if you planted into heavy clay soil, added lots of amendments and left a smooth sided slick hole, there is a possibility that it is not drained well enough and water is collecting in the bottom of the hole like a sump when you water because the native soil is draining at a different rate from your amended soil. Your local nursery staff and/or county extension should be able to tell you if your local soil is likely to respond this way. If so, you may need to change to a better draining site such as a slight slope, or plant the tree on a slight rise, and rather than adding amendments simply loosen the soil over a wide area to encourage the roots to spread out and grow.
I'm sorry you are having trouble with your tree. Sometimes transplant stress causes a tree to defoliate, this late in the season it is not such a serious thing assuming all other factors are favorable. It may be that it will come through just fine and grow next spring -- although severe stress can cause it to not bloom the first year. Since it is just newly planted, I would strongly suggest you consult with the retailer right away about the wilting and also possibly with your county extension. Good luck with your tree!
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