The crepe myrtle (Lagerstroemia indica) is an ornamental tree known for its long, colorful summer bloom period and attractive exfoliating bark. To maximize vibrant flower clusters, a balanced nutrient regimen is often required. Providing specific nutrients, particularly nitrogen, directly supports the vigorous new growth on which the blooms form. Understanding the correct frequency and type of fertilizer encourages a spectacular flowering display each season.
Timing: The Annual Fertilization Schedule
Established crepe myrtles generally benefit from one to three fertilizer applications per year. The initial application should occur in early spring, just before new foliage emerges from dormancy. This early timing ensures nutrients are available to fuel the rapid spring growth necessary for summer flowering.
For trees in poor soil or where maximum growth is desired, a second application can be made in late spring or early summer, six to eight weeks after the first feeding. This second boost helps sustain the plant throughout the peak growing period. However, stop all fertilization by mid-summer (no later than July) to prevent stimulating soft, late-season growth.
Stopping fertilization in mid-summer allows the new wood to harden off properly before colder weather arrives. If fertilization continues too late, the resulting tender growth is susceptible to damage from an early frost. A single application of a slow-release product in early spring is often sufficient for healthy, mature trees in good soil.
Selecting the Right Fertilizer Formulation
Successful fertilization involves selecting a product that supports vigorous growth and heavy blooming. Crepe myrtles require a high amount of Nitrogen (N) because they bloom exclusively on new wood produced during the current growing season. Balanced ratios, such as 8-8-8 or 10-10-10, are widely recommended for general purpose feeding.
Some gardeners prefer formulations with a slightly higher nitrogen content, like 12-4-8 or 18-6-6. Using a slow-release granular formulation is often the best approach for established trees. These products gradually feed the plant over several months, preventing the rapid, weak growth spurts associated with quick-release fertilizers.
While liquid products can be used for more frequent, lighter feeding, slow-release granular fertilizer ensures a steady supply of nutrients. This helps avoid the “leggy” growth pattern that can result from a sudden nitrogen surge. A balanced slow-release formula is a reliable choice for most home gardeners.
Special Considerations for Crepe Myrtles
Newly planted crepe myrtles require a different approach to feeding compared to established trees. To encourage a robust root system, avoid fertilizing new plantings during the first year. Focusing on consistent watering and root development is a higher priority than stimulating top growth.
When applying fertilizer to an established tree, spread the product evenly across the soil surface, covering the area under the canopy (the drip line). Keep the granules several inches away from the trunk to prevent chemical burn to the bark and root crown. After application, thoroughly water the area to dissolve the nutrients and move them into the root zone.
A common issue is over-fertilization, characterized by excessive leaf growth, few or no flowers, and sometimes leaf scorch. Too much nitrogen can lead to lush foliage at the expense of bloom production. Using the recommended amounts for the tree size and sticking to early-season timing minimizes the risk of over-feeding.