Answer: If only the margins of the leaves are black and you see no other spots on the leaves, the problem is probably associated with droughty conditions (or wide fluctuations in soil moisture) or over-fertilization. If you also find spots on the leaves, it could indicate a fungal disease. It's impossible for us to diagnose the problem without actually seeing it so your choices are to pop a few affected leaves into a plastic baggie and take them to your local garden center or Cooperative Extension office for diagnosis, or to wait it out and see if the foliage looks normal in the spring. I suspect that once your trees become well established in their new homes that they will produce healthy foliage which will maintain a healthy green color throughout the summer months. Best wishes with your trees!
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