Cold-hardy hibiscus is a native North American plant also known as swamp mallow. These hardy perennials look similar to their tropical cousins, but they can handle the extreme temperatures of USDA zone 4. They have huge blooms up to 13 inches in diameter to make any garden look like a tropical paradise. Transplant cold-hardy hibiscus in early to midspring.
Choose a planting site with full sun and moist soil.
Pull all weeds from the site and rake any rocks out of the way.
Add 4 inches of compost or manure per square foot of soil to enrich it. Work the compost or manure into the soil to a depth of 5 inches.
Dig around the base of the hibiscus, about 6 inches away from the crown. Loosen the soil under and around the plant, then carefully lift it.
Dig a hole for the hibiscus as deep as the root ball and three times as wide.
Place the hibiscus in the hole. Spread the roots and cover them with soil, allowing the crown to stay above ground level.
Water the hibiscus and keep the soil moist for at least one week.