Answer: I suspect your new tree is adjusting to its new home and is showing a little stress. It's early enough in the season that it will probably replace the leaves that it is losing. To help it become established, be sure to water deeply once each week. It might help to make a watering basin or water well directly beneath the plant by mounding up a few inches of soil all around, about 12" out from the trunk. Fill the basin with water, allow to drain, then fill a second time. Once a week should do it. Watering this way will concentrate the moisture directly over the root mass and will allow it to trickle down, wetting the entire root zone. This will promote deep rooting of your tree. When maple tree leaves are shaded as they develop and then are exposed to direct sunshine, they sometimes turn yellow. The affected leaves will drop but new (and more sun tolerant) leaves will be produced. Just be patient with your tree and it will reward you with healthy new growth.
Best wishes with your landscape!
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