Rose of Sharon not sprouting leaves
My Rose of Sharons in a row. Some are full of leaves, others look dead.
Certified GKH Gardening Expert
Rose of Sharon is hardy to zone 5 and you are in zone 5b, so you are cutting it close. You may have a couple varieties with a slightly different cold tolerance. Plus, Rose of Sharon shrubs are susceptible to winter injury. To tell if they are alive, pull back a branch and see if it is supple or brittle. If it snaps off the branch is dead. Also you can scratch off about 1/2 inch length of bark to reveal the layer below it. If it is brown, the branch is dead. If it is green, it is still alive. If it seems to be alive perhaps they don't get as much sun as the others and are lagging behind. You can try cutting the shrubs close to the ground to see if they will come back from the roots. If you don't see any new growth within a month, then replace them.
Here is more about their care: