The best way is to start controlling tree height long before it grows too large, via careful pruning through the years. But that’s not always possible. If a tree has become too high or too large, use selective pruning to remove the most troublesome branches, one by one, without topping the tree. Gently shaping a tree like this can, over time, correct problems. You can also find growth inhibitors to spray on a tree to stop it from growing too rapidly, but use these sparingly if at all.

Generally, you do not have the right to take fruit from a neighbor's tree, even if the branches overhang your property. The fruit is considered the property of the tree's owner. While you may have the right to trim branches that cross into your yard, the fruit on them typically still belongs to your neighbor. However, laws can vary by state and municipality. In some areas, branches that extend into your yard or trees that straddle a property line may entitle you to some of the fruit. The best course of action is to speak with your neighbor, as they may be happy to share. If a conversation is not possible, check your local regulations before picking any fruit.

The best time to prune Japanese flowering cherry trees depends on where you live and the type of flowering cherry tree. Some trees benefit from being pruned toward the end of winter or early spring, after the last freeze. Meanwhile, other trees do well after blooming, in late spring or early summer. Avoid pruning your flowering cherry tree in the early winter, as this encourages open wounds that can lead to infections or infestations. 

It depends on the problem, the affected part of the tree, the risk of the pathogen spreading, and the overall health of your tree. Many diseases, fungal infections, and insect infestations can be successfully treated, especially if the issue is only in a few branches. However, if a disease is too widespread, too severe, too easily spread, or in the roots, the tree will likely need to be removed.