Last week, I discussed the characteristics and varieties of crape myrtles to try to instill a greater understanding of the species. As shoots develop into twigs, then limbs and then branches, they have leaves spaced along them. The leaves are usually an inch or two apart along the shoot. Where the stem of a leaf, called a petiole, joins the shoot, there will be a lateral bud. Lateral buds give rise to lateral shoots.
Plants control the development of lateral shoots through hormones.
Some lateral buds are allowed to develop into shoots while others are suppressed from development. The details are far more intricate than what I just described, but the logic of this will be clear. Plants produce more lateral buds than what they need so that they can resume growth of shoots and leaves if they become damaged or diseased. These extra lateral buds disappear from view as the limbs and bark become thicker, but they are still there, dormant just under the bark in case they are needed. When crape myrtles are severely pruned back, all the tissue that would normally give rise to growth in the spring is removed.