Answer: The most common reasons for crepe myrtle to fail to bloom are too little sunlight (they need full sun all day long) and/or pruning at the wrong time and/or over supplying nitrogen. They bloom on new growth of the season so any pruning should be done in late winter to very early spring only, pruning in summer will remove flowering wood. It is also possible that overfertilizing, especially with nitrogen, can cause excessive growth at the expense of flowering. This can happen if for example you are fertilizing adjacent lawn grasses with a high nitrogen fertilizer and also fertilizing the crepe myrtles themselves. I hope this helps you trouble shoot.
Q&A Library Searching Tips