You are going to enjoy those Rose of Sharon for years to come.
*Puts on Nursery Manager Hat*
Don’t be stingy on the pruning. They can get ‘leggy’ if they’re not kept in check every few years.
But if you’re NOT going to prune, give them each a lot of room to spread out:
7. Pruning Is Not Required
If you don’t have the time or inclination to prune a rose of Sharon every year or so, rest assured it won’t hurt the plant. This shrub does not require pruning to grow and flower well. Given its speedy growth rate, rose of Sharon will reach its full size in a couple of seasons, so make sure to plant it where it can freely expand. Note that the branches of plants that are not pruned often develop an irregular, somewhat floppy habit, giving the plant an informal appearance.
Good primer here on when and how to prune:
https://www.bhg.com/how-and-when-to-prune-rose-of-sharon-8349539
Thanks! Mom is a ‘champion’ pruner. She can’t pass any bush without ‘snipping’ away to get them into a ‘controlled’ rounded shape. She often prunes when she shouldn’t & cuts off future blooms. At the old house, the azaleas & pomegranate bush didn’t bloom due to being pruned at the wrong time. I have threatened to bury her with a pair of Fiskar pruners on her chest. I am going to print off the pruning guide & see that she sticks to it!
These bushes get 6-10’ wide, per the card that came with them. We are allowing 9’, which should be sufficient space.