Answer: Yellow foliage is normal in the fall, but not in mid-summer. It indicates your birch is under stress - perhaps from the weather, or perhaps from poorly draining soil (which would mimic the stress of over-watering). If you have changed nothing in the routine care of your tree, I would chalk the problem up to weather stress. Your tree may develop new foliage or it may completely defoliate and look terrible the rest of the season. If the leaves dropped because of weather induced stress, it will leaf out normally next spring. If the leaves yellowed and dropped because of root problems, you probably won't see any growth at all next spring. There's really not much you can do except wait and watch. Hope the news next spring in good!
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