Hardy hibiscus is getting rather large..how would you divide it in the spring? I live in Zone 5 in the midwest.
It's best to divide hardy hibiscus while they're still dormant, in late winter or very early spring. At that time you can dig up the entire clump and chop or saw through it. It wll be quite woody, so you may not be able to slice through it with a shovel. Make certain that each division has several growing points on it, and replant where you'd like them.