The best time for the lemon tree would be in October or November. Pruning will stimulate new growth, and will be a target for citrus leaf miners. The moths that lay the eggs aren't active in cooler weather, so pruning in the fall will give the leaves a chance to grow before the moths return in the spring. Citrus leaf miners only affect new leaves that are still soft.

Mock orange, which is a common name given to many different shrubs, isn't really a ctrus tree, so prune it whenver you want.