Hibiscus – can you think of them without imagining idyllic South Sea beaches and dark-eyed Tahitian beauties in bright sarongs?
Coming east from China by way of Polynesia, these striking flowers were embraced by Hawaiians, who made the delicate pale yellow hibiscus known as pua aloalo their official state flower. Associated with royalty and sacred in some cultures, the tropical hibiscus once was thoroughly exotic and rare in mainland America.
Not any more. Sophisticated propagation techniques have made them plentiful and cheap, and tropical hibiscus are now turning up seasonally in garden centers as patio plants for the masses. Shimmering with the colors of a tropical sunset and as prolific as petunias, these tender plants can be discarded at season’s end or overwintered as indoor houseplants.
There is another hibiscus that is perfectly hardy in climates as harsh as Minnesota’s. Hybrids of the North American native rose mallow, Hibiscus moscheutos, are some of the gaudiest hardy perennials you can grow with flowers up to 12 inches across.
True, they have a more limited palette of colors, ranging mainly from the deep reds to blush pink and white, but modem hybridizers are constantly churning out new flower and foliage colors. These plants make a bigger, bolder statement than the more familiar hardy type, Hibiscus syriacus or rose-of-Sharon, a fixture of many older gardens.
No matter which type sings to you, hibiscus are worth knowing and growing for a burst of vibrant color few other plants can match.
The tropical Hibiscus rosa-sinensis has shiny, dark green foliage and 3-inch-to-6-inch flowers in yellow, pink, orange, salmon, red or some intriguing blend thereof. The blossoms can be double, too, a feature of tropical hibiscus alone.
All of these tropicals enjoy a fast-draining fertile soil on the acid side, making peat moss a good soil amendment. These are planted out after all danger of frost has passed in a sunny spot — they want six hours or more of direct sun.
Hibiscus are heavy feeders, and repeated light applications of a general purpose fertilizer is recommended by experts. Regular watering and mulching to conserve soil moisture will keep the plant healthy and the blooms coming.
Many people buy container specimens for the patio and repotting is seldom required as these plants flower best when their roots are somewhat potbound. Having portable plants makes it easy to find the perfect spot with good sun and shelter from breezes that can batter the flowers. Fertilizing faithfully is even more important with container plants, since potting soils often lack essential plant nutrients.
Diseases aren’t usually a problem and pests are rarely troublesome. If plants are plagued by aphids, spider mites, mealy bugs or white flies, be extremely careful about applying insecticides — many can cause a toxic reaction that completely defoliates the plant. Try a strong jet of water to dislodge insect pests or an insecticidal soap.
To learn more about tropical hibiscus, visit the American Hibiscus Society website. It includes a gallery and links to plant sources.
THE HARDY BOYS
Hardy hibiscus are even easier to grow and they can be treated much like any cold-tolerant perennial. These have dull, medium-green heart-shaped leaves and wonderfully large flowers. The entire plant dies to the ground in winter, but just like any hardy perennial, rises anew come spring.
While quite drought-tolerant once established, they also can grow in damp or even soggy soils. Like the tropicals, they prefer a slightly acidic soil and at least six hours of full sun. Flowering begins in mid to late summer and continues until frost.
While there is less variation in the huge flowers, disks 8 inches to 12 inches across, there is more choice in the plant’s ultimate height. Hardy cultivars range from 2 feet to 8 feet, and can make excellent flowering hedges or mingle with other tall perennials like daylilies, Russian sage or ornamental grasses.
Robert Darby bred some of the best-known hybrids, ‘Lord Baltimore’ and ‘Lady Baltimore,’ flowering red and pink respectively on 4-foot-to-5-foot plants. The Fleming Brothers (Jim, Bob and Dave) of Lincoln, Nebraska famously spent 50 years producing dozens of new varieties including ‘Kopper King’ with vivid, copper-red foliage and ruffled white flowers, the purple ‘Plum Crazy,’ and ‘Old Yella,’ the first yellow cultivar
More popular still in recent years are compact forms like the ‘Disco Belle,’ ‘Luna,’ and ‘Splash’ series with a mature height of just 2 feet to 3 feet and outsized flowers in red, pink, blush or white. These smaller forms can be grown in pots, although you will need to get them in the ground by around Labor Day to give them adequate time to prepare for winter.
Hardy hibiscus emerge late in spring — late May or even early June. Give them a fertile soil and water consistently to get them going. Feed them each spring along with other perennials, using a 10-20-10 formula or organic compost, and repeat in midsummer if leaves start to look pale.
Few pests and diseases attack hardy hibiscus, but Japanese beetles may be a problem. Hand pick or use only the same pesticides appropriate for tropicals, since these plants also are sensitive to some chemicals.
Once frost kills upper growth, trim stems back but leave 8-inch-to-10 inch stalks so you can avoid disturbing them before they sprout next spring. Because they emerge so late, hardy hibiscus are good companions for small early spring bulbs, whose dying foliage will be concealed by their fast-growing sprouts.