Q.Is It Too Late to Prune 4 Year Old Rose of Sharon
Is it too late to prune a 4-year-old rose of sharon?

No, it is not too late. But, I suggest waiting until late spring to do heavy pruning. If part of the plant is hanging over a heavy traffic area, you can do selective pruning as needed. Since Althea or Rose of Sharon blooms on new growth, you just shouldn't prune in mid to late summer. You also don't want to prune too close to oncoming cold weather. If the plant were to start growing after being pruned and there is a cold, freezing snap befofre the new growth hardens off, the plant could be damaged.