Rose Mallow

Rose mallow (Hibiscus moscheutos) is a tall herbaceous perennial with large flowers, up to 20 cm across, in white, pink or pinky-red, sometimes with a dark eye. Plants can reach about 4.9 to 8.2 feet (150 to 250 cm) tall and about 1.6 to 3.3 feet (50 to 100 cm) wide. It is native to southern and eastern North America. Each flower lasts only a day, but a plant may open several at once. Plants die back to the ground in fall and come back the following spring.

Bloom timing differs between sources: one gives July through September, while another gives August to October.

Start seeds indoors about 12 weeks before the last spring frost. Soak the seeds overnight before sowing. You can also sow seed directly outdoors after the last expected frost date. Plants started very early in spring can flower the first year from seed.

Site and soil. Grow rose mallow in full sun in neutral to slightly acidic, rich, well-drained soil. One source lists full sun to partial shade as suitable.

Growing time. Plants take 2 to 5 years to reach their full size. Hibiscus need long, hot summers to flower well.

Other propagation. You can also propagate by division in spring. Divide only in spring, since plants do not usually tolerate fall division or transplanting.

Water. Keep the soil consistently moist, since rose mallow prefers rich, moist soil and grows in wet areas. Plenty of water is needed for the most blooms.

Feeding. These are heavy feeders, so fertilize in spring.

Pruning. Little pruning is usually needed. Cut old stems back to about 8 to 15 cm (3 to 6 inches) above ground in late winter or early spring.

Winter. Mulch well over winter. Winter mulch may be needed in colder areas.

Plants may be attacked by aphids, scale insects, mealybugs and whitefly, mainly when grown under glass. Japanese beetles are also listed as insect pests of hibiscus in general.

Leaf spots caused by several fungi can occur; in most cases, removing plant debris and infected leaves provides adequate control. Powdery mildew may occur, and honey fungus is rare.

To help prevent southern stem blight, keep mulch away from the stems.