The Crepe Myrtle (Lagerstroemia indica) is a popular ornamental tree known for its vibrant summer blooms, but it can cause considerable anxiety for gardeners in the spring. Unlike many deciduous trees that burst into leaf at the first sign of warm weather, the Crepe Myrtle is one of the last to wake up. This delayed emergence is a natural, protective mechanism that often leads people to worry their tree has not survived the winter.
The Standard Timeline for Zone 7 Leaf-Out
Zone 7 is defined by average minimum winter temperatures ranging from 0°F to 10°F, which is a suitable climate for Crepe Myrtles. The species is cautious about breaking dormancy too early. The standard window for leaf-out in Zone 7 typically begins in late April and can extend into mid-May.
It is entirely normal for a Crepe Myrtle to remain completely bare long after maples, oaks, and other trees have fully leafed out. The tree prioritizes the production of roots and internal wood structure over leaf growth during the initial spring warming period. This strategy helps the plant build strength before committing energy to vulnerable foliage.
In cooler spring seasons, or if the tree is newly planted, leaf-out may not occur until late May or even the first week of June. The tree is waiting for sustained warmth, not just a few sunny days. Seeing buds swell and tiny green points appear is the first indication that the tree’s winter sleep is ending.
Understanding Dormancy and Temperature Triggers
The delay in spring awakening is controlled by a biological process called endodormancy, which is the tree’s internal rest period. This deep dormancy must be broken by a sufficient period of chilling temperatures in the winter. Once the chilling requirement is met, the tree then waits for specific, sustained warmth cues to begin growth.
The critical factor controlling leaf-out is often soil temperature, not just air temperature. Crepe Myrtles require the soil around their roots to warm consistently above 60°F before they push new growth. Air temperatures fluctuate quickly, but soil temperatures rise slowly and remain more stable, providing a reliable signal that the threat of a late freeze has passed.
A mild winter followed by a sudden, late-season cold snap can sometimes further delay the process. If the tree starts to break dormancy during a warm spell and is then hit by freezing temperatures, the developing buds can be damaged. The tree must then divert energy to producing a secondary flush of growth, which pushes the leaf-out date even later into the season.
Assessing and Troubleshooting Late Leaf-Out
If your Crepe Myrtle has not leafed out by mid-June in Zone 7, it is time to perform a simple assessment to check for viability. The most reliable method is the scratch test, which involves gently scraping a small section of the bark on a branch. If you see a bright green layer of tissue directly beneath the outer bark, the branch is alive and simply delayed.
If the tissue underneath is brown and dry, that specific section of wood has died, but the entire tree may not be lost. Continue scratching down the branch toward the trunk until you locate green tissue or reach the base. Damage is sometimes limited to the tips, or in severe cold events, the tree may have died back to the ground but will regenerate from the root crown.
Failure to leaf out can be caused by severe winter damage, especially if temperatures briefly dipped below the 0°F threshold for an extended period. Another common cause is improper, aggressive late-season pruning, often termed “Crepe Murder,” which can stress the tree and inhibit its ability to recover effectively. Underlying issues like root stress, poor drainage, or disease are less common but can also prevent a spring emergence.
If the scratch test shows green tissue at the base and the root crown appears healthy, continue to wait and provide basic care, such as watering during dry spells. If the tree remains dormant past the end of June, or if the scratch test reveals brown tissue all the way to the ground, consult an arborist or consider replacing the plant. Most often, the Crepe Myrtle simply requires patience, waiting for conditions that ensure its long-term survival.