While a trip to a tropical paradise may not be in the family budget, you can create a garden with a lush, exotic feel even in climates with subzero winter temperatures. Perennial hibiscus plants -- rose mallow (Hibiscus moscheutos), swamp mallow (Hibiscus coccineus) and rose of Sharon (Hibiscus syriacus) -- sport the same oversized, brightly colored flowers as their tropical counterpart (Hibiscus rosa-sinensis), which is suitable only for U.S. Department of Agriculture plant hardiness zones 9 through 11, but can bounce back from winters down to USDA zone 4, depending on species. While perennial hibiscus species tend to be tough, a little pampering in the fall can ensure you'll have them around to enjoy all summer.
1 Wipe down the blades or your hand pruners or loppers with household antiseptic cleaner to ensure no lingering plant disease or fungal spores can infect your perennial hibiscus. Dry the blades with paper towels.
2 Cut the stems down by one-half to two-thirds their height in fall as blooms fade if your perennial hibiscus is in moist, rich soil and volunteer seedlings are a problem. The colder your winter climate, the taller you should leave the stems, removing just the upper portions to avoid rampant self-seeding, which can be a problem with some varieties in moist soil. The stems provide insulation to the crown of the plant -- cold damage tends to start at the top of a plant and move down, so the more plant material above the crown, the better.
3 Apply a 4- to 6-inch layer of straw or chopped leaf mulch over the crown and root zone of your perennial hibiscus -- even if you did not prune it in the fall -- after a freeze. Mulch isn't meant to keep the ground warm, but to protect it against temperature fluctuations that can bring a plant out of dormancy too early, or cause soil heaving.
4 Pull back the mulch in mid- to late spring as temperatures start to warm. Perennial hibiscus are notorious slow starters in the spring and may not show signs of life until the soil temperature is at least 70 degrees Fahrenheit.
5 Cut all stems down to within 6 to 12 inches of the ground in early spring when new shoots emerge from the ground or buds start to swell low on the stems. It is normal for many of the stems left on a perennial hibiscus to die back to the ground.