Lagerstroemia indica, commonly known as the crape myrtle, is a highly favored ornamental shrub or small tree, prized for its vibrant summer flowers and attractive bark. While a crape myrtle will not die if left completely unpruned, neglecting this maintenance results in specific, predictable changes to its appearance, health, and flowering performance. These outcomes are a natural expression of the tree’s biology, differing significantly from the manicured look many homeowners expect.
Changes to Natural Form and Size
A crape myrtle that is never pruned will revert to its innate, more shrub-like growth habit, developing a dense, multi-stemmed structure. The tree will naturally grow taller and wider, often exceeding the size intended for its landscape location. This increase in dimension can cause the plant to intrude upon structures, walkways, or other nearby plantings.
The canopy of an unpruned tree becomes significantly thicker and more congested due to the accumulation of many years of new growth. This results in a heavy, bushy appearance, with new shoots emerging at the tips of old wood. Over time, the lower portions of the plant may become “leggy,” with much of the foliage and branching concentrated at the top due to competition for sunlight.
Impact on Flowering Quality and Location
Crape myrtles produce their spectacular summer blooms exclusively on new wood, meaning the current season’s growth. When the tree is not pruned, the energy that would normally be focused into producing fewer, stronger new shoots is instead spread thinly across a multitude of older, secondary branches. This distribution of energy results in flower clusters that are noticeably smaller and less concentrated than those found on properly maintained specimens.
Furthermore, as the tree gains height, the bloom-bearing new growth shifts upward, making the flowers less visible and less impactful from eye level. The vibrant display is essentially lifted high into the canopy. The tree still flowers, but the overall presentation is diminished, with blooms scattered across the expansive, unmanaged structure.
Structural Weakness and Increased Disease Risk
An unpruned crape myrtle develops a dense interior structure, restricting airflow through the canopy. This poor air circulation traps moisture and humidity, creating a microclimate ideal for the proliferation of fungal diseases. The most common of these is powdery mildew, which manifests as a white, dusty coating on leaves, buds, and new shoots, often leading to discoloration and stunted growth.
Structural problems accumulate as branches are left to grow unchecked. Unwanted branches often cross and rub against each other, creating friction points that wear away the bark. These open wounds serve as easy entry sites for wood-decaying fungi and various insect pests. The lack of thinning also means that branches are more susceptible to snapping under the weight of heavy ice, snow, or saturated flower clusters.
Steps for Managing an Unpruned Tree
For a crape myrtle that has been neglected for several years, a severe cut, sometimes called “crepe murder,” is not the recommended solution. Instead, the goal is a multi-year restoration process focused on thinning and improving structure. Begin by removing all suckers from the base of the tree and any small, twiggy growth inside the main canopy.
The next step involves selectively removing crossing branches and those growing inward to open up the center of the tree and improve air circulation. If height reduction is necessary, it should be done gradually over two to three dormant seasons by cutting back to a strong lateral branch. This measured approach maintains the tree’s natural form while restoring its health and maximizing its ornamental value.