When do you trim rose of sharon and how do you do it?

I prune mine in the autumn after it is finished blooming. I take out all of the crossed branches, stragglers and suckers. But, for the first few years after planting it, I left the suckers on the base so that it could fill out and get bushier. I haven't had any dead branches on either of the plants I have, but if you do prune those out. I'm letting mine grow taller so I merely shape the top until it gets to the height of the fence and then I will keep it at that height. I use bypass pruners to cut off the branches.