When it comes to hibiscus (Hibiscus spp.), you'll find no mystery to pruning. All species bloom on new wood, so they are pruned in the spring. You also don't need to worry about the type of cut to make and where to snip -- the whole plant is cut back near the ground. Tropical hibiscus (Hibiscus rosa-sinensis) can be grown outdoors year-round in U.S. Department of Agriculture plant hardiness zones 8 to 11, while perennial hibiscus such as rose mallow (Hibiscus moscheutos) are hardy from USDA zones 5 through 10. In areas of those zones that experience freezing temperatures, Mother Nature even does some of the work for you, killing the stems back to the ground every winter.
Spray the blades of your pruning tools down with household antiseptic cleaner, and wipe them dry with paper towels. This cuts the chances of spreading a plant disease or fungus to your hibiscus from another plant you pruned with the tools.
Examine perennial hibiscus and outdoor tropical hibiscus in early spring. Look for buds or swellings near the horizontal leaf scars at the base of the stems on the plants or for coming coming up from the root zone. In any area that's experienced a killing frost, stems may be dark and brittle all the way to the ground. Cold damage kills from the top down. You can often tell where winter dieback ends on a stem by a lightening in color on the wood that is still good or by scratching the bark with your fingernail. If you see green, it is still alive.
Cut each stem back to within 6 inches of the ground. Remove any stems that have died back all the way at the base. Use hand pruners for stems up to 1/2 inch in diameter and loppers for shoots from 1/2 inch to 1 1/2 inches thick.
Remove dead and crowded branches at the base from tropical hibiscus overwintered indoors, and those that stayed outdoors and didn't get hit by frost. Even if these didn't die back, they won't bloom as much if they aren't pruned.
Cut the entire plant back by one-third to one-half, making the cut at a 45-degree angle just above a leaf so the stubs don't show. Cut them to within a few inches of the ground if all of their leaves dropped over winter.