Depending on variety, Crapemyrtles can be grown from USDA hardiness zones 6 to 10. In zone 6, even the most cold-hardy varieties will probably be killed to the ground each winter and will be useful only as a shrubby, flowering perennial. They are better adapted to the more humid regions of the country, but will grow in arid climates with supplemental irrigation during dry periods.
Crapemyrtles require moderate to well-drained soils. They can be grown in clay, loam or sandy soils as long as the soils are oxygenated. The soil pH should be 5.5 to 7.5 with 6.5 being optimum.
For superior flowering, they require full sun, a minimum of six hours per day. They will grow in a shaded environment, but will not be as full, and flowering will be diminished or non-existent.
Crapemyrtles are quite drought tolerant once they have become established; however, supplemental watering during dry spells will provide better growth and flowering. Using a three to four inch layer of mulch out to the drip line of the tree will help modify the soil temperature, and will help conserve soil moisture.
Newly planted trees should be watered one to five times per week depending on the time of year they are planted, and the type of soil. If they are planted during the dormant season (the preferred time for zones 7 to 10), they need to be watered once each week depending on soil moisture levels. The root system will continue to grow during the winter months. Planting during the hotter times of the year, a new tree in a sandy soil may need water almost daily if we have no rain.
Until Crapemyrtles reach maturity, they will benefit from annual fertilization. With very young trees, you may wish to fertilize twice each year and then cut back to once per year when they begin flowering well.
The first fertilization should be done in early spring just as the new leaves are emerging. If it is fertilized a second time, do this two months later.
Use a complete fertilizer which contains nitrogen, phosphorus and potassium. A fertilizer with a 4:1:2 or 2:1:1 ratio should provide adequate results, but having your soil analyzed would allow you to select the fertilizer that provides exactly what is needed.
Using a slow-release fertilizer will provide nutrients over a longer time. This will prevent overly-succulent growth that may be more susceptible to insects and diseases.
After you have chosen the right site that has good light, good drainage, and room to grow, planting a Crapemyrtle is the same as with almost any tree or shrub:
1. Dig a hole that is the same depth as the root ball and is at least twice the diameter.
2. If the tree is balled and burlapped, lift plant into the planting hole using the lifting strap on the wire basket. Do not lift by the trunk. Once in the hole double check that the top of the root ball is level with or slightly above the surrounding grade. Remove all straps or twine. Large trees will usually have a wire basket which supports the root ball. This basket should be cut from the top and at least 1/3rd the way down the sides of the root ball. Pull out the pins holding the burlap and remove the burlap from the top of the root ball. The burlap can be folded beside the rootball, but it is best to cut and remove it down to the remaining wire basket.
3. If the tree is in a container, first make sure the root ball is moist. If it is dry, water the plant before you remove it from the container. Look at the roots on the outside of the root ball. The roots need to be disturbed in a way to encourage them to quickly grow out into the soil. The roots can either be teased out with your fingers or lightly cut with a knife. If cutting with a knife, avoid severing large roots which will have many feeder roots growing from it. Place the plant in the hole and check to see that the top of the root ball is level with or slightly above the surrounding soil.
4. Backfill with the native soil about 1/3rd of the way and lightly tamp. Step back and see that the tree is not leaning. Continue to backfill and firm the soil. Make sure that no additional soil is put on top of the root ball. Use the leftover soil to create an earthen basin just outside of the rootball.
5. Water the tree thoroughly to settle the soil. Mulch with an organic mulch to the depth of three to four inches. Keep the mulch a few inches away from the trunk to allow good air circulation. After one growing season, remove the water basin.
6. It is usually unnecessary to stake trees unless the site is extremely windy. If the trees need to be staked, check the wires every month to make sure they are not girdling the trunk and remove after one growing season.