The Osage Crepe Myrtle (Lagerstroemia indica x fauriei ‘Osage’) is a distinguished hybrid prized for its resilience and striking appearance. Developed at the U.S. National Arboretum, this cultivar combines the intense summer flowering of L. indica with the superior cold hardiness and disease resistance of L. fauriei. The tree matures to about 16 feet with an upright, spreading habit, showcasing large clusters of vibrant pink blooms from early summer through fall. It offers year-round interest with its smooth, exfoliating bark, which peels away to reveal attractive shades of light and dark brown.
Selecting the Best Location and Planting
The successful establishment of an Osage Crepe Myrtle begins with choosing a location that provides ample sun exposure. This variety requires a minimum of six hours of direct sunlight daily to produce its best flowers. Planting in a shaded area will significantly reduce the number of blooms and may lead to a spindly growth habit.
The ‘Osage’ is tolerant of various soil types but thrives best in a site with excellent drainage. Consistently soggy conditions can lead to root issues, so the soil must not retain standing water. A slightly acidic soil pH, ideally below 6.5, is preferred. Alkaline conditions can sometimes induce chlorosis, a condition causing the leaves to yellow.
When preparing to plant, dig a hole that is only as deep as the root ball but two to three times as wide. This width allows the new roots to easily expand into the surrounding, loosened soil. Gently remove the tree from its container and inspect the root system. Use shears to clip any thick, circling roots that may girdle the plant.
Place the root ball in the center of the hole, ensuring the top is level with or slightly above the surrounding grade to prevent water from pooling at the trunk. Backfill the hole with the original soil, tamping gently to remove any large air pockets that could dry out the roots. After planting, provide a thorough, deep watering.
Essential Year-Round Maintenance
Consistency in watering is essential for the first two growing seasons after planting. Newly planted trees should receive deep watering at least once a week, or twice during periods of extreme heat or drought, to encourage a robust root system. Deep watering means soaking the soil in the root zone slowly until it is saturated, which is more beneficial than frequent, shallow sprinklings.
Once the tree is well-established, the ‘Osage’ becomes remarkably drought-tolerant and requires far less supplemental irrigation. Mature trees only need deep watering during extended dry spells, particularly when they are actively blooming.
Fertilization should be approached conservatively. For the first year, a slow-release, balanced fertilizer can be applied once a month during the spring and summer to support growth. After initial establishment, a single application of a slow-release, acid-loving fertilizer in early spring, just before new growth appears, is generally sufficient.
Applying a three-to-four-inch layer of organic mulch around the base of the tree helps to conserve soil moisture, regulates soil temperature, and suppresses competing weeds. Keep the mulch pulled a few inches away from the trunk itself to prevent moisture build-up. Moisture build-up can lead to decay and insect issues.
Shaping the Osage Crepe Myrtle Through Pruning
Pruning the Osage Crepe Myrtle is best performed during the late winter or very early spring while the tree is dormant, just before new buds begin to swell. Pruning at this time will maximize the season’s flower production. Pruning should focus on thinning the canopy to improve air circulation and maintaining the tree’s natural, graceful form.
Severe topping, often called “Crepe Murder,” involves cutting main branches back to thick stubs. This practice ruins the tree’s structure, creates unsightly knots, and forces weak, whip-like growth. This weak growth is less able to support the heavy flowers. Instead, focus on removing dead, diseased, or broken branches first, cutting them back to the branch collar or the point of origin.
Next, remove any crossing or rubbing branches that could create entry points for disease or damage the bark. To showcase the attractive exfoliating bark, remove small, twiggy growth and suckers that sprout from the base of the trunk or along the lower portion of the main stems, typically up to five feet from the ground.
Identifying and Managing Potential Problems
Due to the inclusion of L. fauriei genetics, the ‘Osage’ exhibits high resistance to powdery mildew. Powdery mildew is a common fungal disease that plagues many older L. indica varieties. This resistance reduces the need for chemical treatments and keeps the foliage looking clean throughout the summer.
Although generally tough, the ‘Osage’ may occasionally encounter common garden pests. Aphids are small, soft-bodied insects that feed on new growth, sometimes leaving behind a sticky residue called honeydew. A strong jet of water from a hose can often dislodge light infestations, or a horticultural oil can be used for heavier outbreaks.
Insufficient sunlight will directly reduce bloom count, as the plant cannot generate enough energy to produce flowers. Similarly, yellowing leaves in the summer, especially with green veins, may indicate the soil pH is too high. High pH locks up essential micronutrients like iron. Addressing these environmental factors is the most effective way to restore the tree’s health.