Crape myrtle (Lagerstroemia indica) is a deciduous member of the loosestrife family commonly grown as a lawn accent, highway plant or garden ornamental. The plant is cherished for its remarkably long bloom period, which can last up to 120 days in ideal conditions. Though generally problem free, crape myrtle is susceptible to several issues that may mar the beauty of the tree.
Failure to Bloom
Several factors can cause a crape myrtle to produce few flowers, or no flowers at all. Crape myrtles require a full day of sunlight in order to bloom profusely, at least six to eight hours per day. Plants may also flower poorly if not irrigated regularly, especially during hot summers. Though crape myrtle thrives if fertilized annually with a balanced fertilizer, using a fertilizer that relies too heavily on nitrogen can result in an excess of foliage, and few blooms.
Crape myrtle is highly susceptible to aphids, which attack from May to September, peaking in the summer months. Aphids feed on foliage and new growth, extracting plant sap and leaving telltale holes and yellowish spots on the plant. Aphids also leave excrement that attracts a mold known as black sooty mold. Control aphids by washing the plant with soapy water, or by using an insecticidal soap. Predatory insects are also effective.
Cercospora leaf spot and powdery mildew are two common fungal diseases that can harm crape myrtle. Cercospora leaf spot occurs in hot, humid weather, causing unattractive spots on the plant's foliage. Control with a fungicide containing thiophanate-methyl. Powdery mildew causes a fine gray dust to appear on the plant's foliage, sometimes suppressing flowering. Plant mildew resistant cultivars whenever possible, and follow proper cultural practices. Lagerstroemia indica x fauriei hybrids are known to be resistant against powdery mildew.
Crape myrtle plants that are growing poorly may attract Spanish moss and lichen, both of which can grow over the plant's branches. Though not especially harmful, the presence of Spanish moss or lichen indicates that the plant is not healthy. Lichen will often go away once the plant's growth begins to pick up. Pick off Spanish moss by hand if needed. Keep the plant healthy by fertilizing with a balanced fertilizer, and watering in times of drought.
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