How do I increase blossoms on a crape myrtle?
Crape myrtle blooms on new growth from the current season. Therefore, the answer to increasing the amount of bloosoms lies in increasing the amount of foliage in the current year.
Feeding the tree as soon as it leafs out with a general fertilizer such as 5-10-5 will promote growth.
Pruning in late winter will help maintain the crape myrtle's shape and increase the amount of foliage. Pinching back the tips of new growth will also increase the amount of foliage, but do not do the pinching if flower buds are present.