Answer: Rose of Sharon needs full sun to grow and bloom its best. It blooms on new growth of the season. It usually begins to bloom in mid summer and continues until frost so it is still early to be looking for it to flower.
The most common causes for lack of bloom are planting it in too much shade, and pruning at the wrong time. Since it blooms on new growth, the only "safe" time to prune is late winter/early spring. At that time you would prune off any winter killed branches and possibly also to shape the plant. Pruning later in the summer will remove flowering wood and flowerbuds.
If your plant is forming flower buds that do not open, there may be an insect problem such as a budworm infestation. If you think this is what is happening, I would suggest you consult with your local Purdue county extension for a more specific diagnosis and based on knowing that, decide how to proceed. If a chemical control is needed, they will have the most up to date information on what to use and how/when is best to use it for maximum results.
Good luck with your Rose of Sharon shrubs this summer!
Q&A Library Searching Tips