Blue Chiffon rose of Sharon blooms on “new wood”, meaning it forms its flower buds on the new growth the same year it blooms. Though heavy pruning shouldn’t be needed, the best time to do so is in early spring. We typically recommend trimming back no more than 1/3 of the stems so the shrub maintains a strong woody framework and enough foliage to make food for the roots.
If you are concerned that your rose of Sharon is going to outgrow its space, it’s better to transplant it to a larger spot in spring rather than prune it severely to try and limit its size. If you need something smaller, consider planting the 3-4’ tall Lil’ Kim® Violet rose of Sharon instead.
When you prune your rose of Sharon in spring, that’s also a good time to scratch some granular plant food formulated for trees and shrubs into the soil. Doing so will encourage it to start the season off strong. No additional feeding is necessary throughout the year.
You will notice that your rose of Sharon shrub tends to leaf out later in spring than many other plants. This is perfectly normal and not a cause for concern. It’s just how Hibiscus rolls. It makes up for its tardiness with exuberant growth in summer.