Hardy hibiscus (hibiscus moscheutos) is more commonly known as rose mallow. It is a perennial shrub that usually grows to be about four feet tall and three feet wide. It has white flowers that bloom in the spring and summer. Hardy hibiscus often are divided to propagate new shrubs or to reduce size. Divide your hardy hibiscus in early spring, just as the new sprouts begin to grow. Replant the divided bushes in full sun and in soil that drains well.
Dig a wide circle around your shrub, at least six inches from the base. That will penetrate some of the roots, but that is expected. The size of your hardy hibiscus will determine how deep you need to dig. It's better to go too deep, so start off a couple inches deeper than you originally planned.
Lift the shrub out of its hole. Lay it on its side and think about how you're going to divide your plant. Separate the shrub into smaller clumps or larger clumps. Just be sure you get some roots with each clump.
Divide the bush with your hands. You may need an axe or saw to cut through the roots. The divided shrubs are now ready to give away or replant.
Plant your new bushes as soon as possible (keep the roots moist in the meantime) to the same depth they were planted originally. Hardy hibiscuses prefer full sun and can tolerate most soil conditions. They do however, prefer soil that is well draining, so consider adding a couple inches of organic matter, such as compost or peat moss, to the soil before planting.