Culture
Easily grown in average, medium to wet soils in full sun. Best in moist, organically rich soils, but does surprisingly well in average garden soils as long as those soils are not allowed to dry out. Regular deep watering is advisable. Immune to the heat and humidity of the deep South. Tolerates some light shade, but full sun with good air circulation produces the best flowers, the strongest stems and the best environment for resisting potential diseases. Site in locations protected from wind to minimize the risk of wind burn. Pinch back growing tips when they reach 8” and again at 12” if bushy plants are desired. Deadhead individual flowers to maintain plant appearance. Cut back stems to approximately 3-4 inches in late autumn. New growth shoots are slow to emerge in spring. However, once new growth begins, it proceeds quite rapidly. Plants will benefit from regular fertilization during the growing season.
Noteworthy Characteristics
Hibiscus moscheutos, commonly known as hardy hibiscus or swamp rose mallow, is a vigorous, sturdy, rounded, somewhat shrubby, hairy-stemmed, woody-based perennial of the mallow family. It typically grows to 3-7’ tall and to 2-4’ wide. Each flower has a prominent and showy central staminal column of white to pale yellow anthers surrounding an even longer style. Individual flowers last only 1-2 days, but new flowers open each day in rapid succession over a long July to September bloom period. At the peak of bloom, a large plant can produce 20 or more flowers per day. Flowers (to 6-9” wide) are among the largest flowers produced by any perennial that is winter hardy. Alternate, broad-ovate to lanceolate leaves (3-8” long) with toothed margins are green above and white-hairy beneath. Leaves are lobeless or have 3-5 shallow lobes. Seed capsules will float on water which facilitates seed dispersal.
Potential Problems
Some susceptibility to leaf spots, blights, rusts and canker. Japanese beetles can severely damage foliage if left unchecked. Whiteflies, aphids and scale are occasional insect visitors. Leaf scorch will occur if soils are allowed to dry out. Healthy plants grown in the proper environment usually do not need staking.
Uses
Moist borders. Specimens. Useful in low spots or wet areas in the landscape. Effective along streams or ponds. Temporary summer screen or hedge. Can be grown in large containers.