Answer: Water stress can cause new growth to droop. Over-fertilization can prompt rapid growth, but the tree has trouble forming bark, which will make the branches and stems more likely to droop during hot weather, especially when it is experiencing water stress (either too much or too little water). Don't fertilize or use any more lime; instead, water deeply once each week. You can build a watering well or watering basin beneath the tree. Fill the basin with water, allow to drain, then fill it a second time. This will concentrate the moisture over the rootmass and allow it to trickle down and wet the entire root area. Do this once a week and your birch tree should be happy.
Best wishes with your tree!
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