Timing is almost everything when it comes to pruning crepe myrtle trees. A gardener shouldn't prune too early or too late in the season. Removing the right growth is also important when pruning crepe myrtle, as is using the proper pruning tools, such as a hand pruner for narrow twigs and a pruning saw for thick branches. It is also possible to over-prune a crepe myrtle, which can make it difficult for the tree to grow back to the right shape.
In most areas, the best time for pruning crepe myrtle is in late winter or very early spring. Pruning a crepe myrtle tree early in the winter, for example in December or even November, may encourage the tree to produce new growth and even bloom in winter if the weather warms up for a spell. If the tree produces growth in the freezing months, however, it can lead to damage to the tree, as the tree should not be active when the weather is cold.
Waiting until the middle of spring to prune crepe myrtle isn't a good idea either. As the weather warms, the tree will grow leaves, which can make pruning crepe myrtle difficult, as the gardener won't be able to see where to cut. A gardener should prune before the tree begins to produce new growth.
When pruning crepe myrtle, the suckers on the bottom of the tree trunk should be cut off first. The suckers pull energy away from the rest of the tree, potentially causing it to not bloom and grow fully on the top. If there are any low branches coming off of the main trunk, they should be cut away next.
A gardener needs to use the proper tools when pruning crepe myrtle. Hand pruners are perfect for branches and stems less than 1/2 inch (1.27 cm) thick, while a pruning saw should be used on very thick stems, those more than 1.5 inches (3.8 cm) wide. Loppers are suitable for branches in between.
It is possible to cut back a crepe myrtle too much, which will damage its growth in the coming year. Ideally, a gardener won't cut the stems to a length shorter than 6 inches (15 cm) and won't cut stems that have another stem growing out of them unless the entire branch is dead. At each cut, two new stems will grow. As it can become crowded in the center of the tree, a gardener may prune branches that grow toward the center a bit more than branches on the outside of the tree.