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. Deep and consistent watering is advisable. Tolerates some light shade, but full sun with good air circulation produces best flowers, strongest stems and the best environment for resisting potential diseases. Site in locations protected from wind to minimize risk of wind burn. Deadhead individual flowers immediately 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 and plants will benefit from regular fertilization during the growing season. May be propagated by division or cuttings.
Noteworthy Characteristics
Hybrid hardy hibiscus are vigorous, sturdy, erect but sometimes shrubby, woody-based perennials that typically grow to 4-8’ tall. Hybrid hardy hibiscus cultivars are often the result of complex breeding work involving multiple species native to the U.S., including H. coccineus, H. laevis, and H. moscheutos. Hybrids are winter hardy to USDA Zones 4 or 5 which significantly distinguishes them from the many tropical to semi-tropical hibiscus on the market today. Each disc-shaped flower (to 6-10” across) features five flat showy overlapping petals (each to 3-4” long) in a variety of colors which surround a prominent and showy central staminal column. Individual flowers remain in bloom for only one day, but one or more flowers usually open each day, in succession, over a long mid-summer to early fall (sometimes to first frost) bloom period. Each plant can produce up to 250 flowers per growing season. Heavily, deeply-cut, irregularly serrate, glossy dark green leaves have reddish stems.
Genus name is the old Greek and Latin name for mallow.
'Turn of the Century' is a very tall, vigorous, sturdy, erect but somewhat shrubby, woody-based hibiscus hybrid cultivar that typically grows 6-8' high and features dinner plate-sized, 5-petaled, hollyhock-like flowers (to 5-9" diameter) which are among the largest flowers produced by any perennial which is hardy to the St. Louis area. Flowers are bicolored (each petal is pinkish red on one side fading to light pinkish-white on the other) with red centers. Flower colors produce an unusual pinwheel-like effect. Each flower has a prominent, pale yellow, tubular central staminal column. Unlobed, ovate, green foliage.
Problems
Some susceptibility to leaf spots, blights, rusts and canker. Japanese beetles, sawflies, whiteflies and aphids are occasional insect visitors. Japanese beetles can severely damage foliage if left unchecked. Leaf scorch will occur if soils are allowed to dry out. Healthy plants grown in the proper environment usually do not need staking. Deer tend to avoid this plant.
Uses
Borders. Specimen, group or mass for landscape accent. Temporary hedge. Useful in low spots or wet areas in the landscape. Effective along streams or ponds.