Crape myrtle is appreciated for its strong, muscular trunks and its panicles of crepe-like flowers. An easy-care small tree, crape myrtle benefits from occasional fertilization.
Nutritional requirements for crape myrtle are usually minimal, but a light spring feeding optimizes growth and flowering. Trees that lack vigor, especially those in poor soil, require an annual feeding in spring and summer.
Look for a fertilizer with a large amount of phosphorus, such as 5-10-5. Phosphorus helps with flower production. For stubborn crape myrtles that won't bloom, use super phosphate, a soil additive product, in conjunction with spring and summer fertilizer applications.
Fertilize crape myrtles in spring as the leaf buds start to grow. If trees are planted in poor soil, give them another feeding in summer when the flowers begin to fade. To keep fertilizer granules from washing away, lightly scratch them into the mulch.
Crape myrtle performs best in full sun -- the more the better. Snipping off faded blooms in summer encourages repeat blooming. Keeping leaves dry by watering at ground level discourages mildew and keeps blooming stems from drooping over from the added weight.