What is the reason why Lagerstroemia indica doesn't blossom very much?

The main reasons why Lagerstroemia indica does not bloom are: 1, and long-term water accumulation in the roots leads to root rot and inhibits the growth of hands. Or the soil is dry for a long time, and the growth of branches is seriously inhibited, not only flowering, but also not bright. 2. Too much nitrogen fertilizer in the soil leads to long branches and affects reproduction and growth. I haven't trimmed it for a long time. Osmanthus fragrans was planted on the branches of that year. If not pruned for a long time, the proportion of dead branches, ineffective branches and weak branches will increase, and the distribution of nutrients in plants will be too scattered, so that new branches cannot germinate and flowering will be seriously inhibited. 4. Pests. Branches and leaves are seriously damaged by pests, and coconut leaves are rarely preserved, which affects flowering.