For the week of August 12, 2002.
Hardy Hibiscus for a Tropical Look
By Linda Naeve
(Every week a plant or landscape item will be featured as "Reiman's Pick." You can see the featured plant or item at Reiman Gardens - just look for the red "Reiman's Pick" signs in the Gardens.)
Garden catalogs often give glamorous, colorful descriptions of the plant varieties they sell. Sometimes they even stretch the truth a bit. For example, Iowa gardeners would consider a plant described as both "hardy" and "tropical" as something of an oxymoron. This week's Reiman's Pick -'Disco Belle' hibiscus - is just that. Not only is it hardy in zone 4, it has a tropical, exotic look.
Hardy hibiscus, Hibiscus moscheutos, is sometimes referred to as rose mallow. It is a distant cousin to cotton, okra and hollyhocks. However, except for the flower shape - the characteristic bell-shape flowers with five petals and a long tubular column in the center - there isn't much resemblance between them. The flowers on hardy hibiscus are six to 12 inches across. Its huge flowers are impressive, and the constant supply of blooms makes it a good addition to many gardens. Individual flowers last only one day, but are produced continuously through late summer until the first fall frost.
Hibiscus can be found for sale each spring at many garden centers. The challenge is differentiating between the hardy and the truly tropical hibiscus at the greenhouse. If a hibiscus plant has glossy deep green leaves, three to six inches across, flowers of salmon, peach, double flowered orange, and double or single flowered yellow, it is probably a tropical hibiscus. Hardy hibiscus do not come in these colors or in doubles. Many tropical hibiscus flowers have more than one color in a bloom either in bands or as spots. If a hibiscus has dull green, heart-shaped leaves, dinner plate-sized white, pink or red flowers with large two- to four-inch buds, it is a perennial, hardy hibiscus.
Plant hardy hibiscus where it will get at least five hours of sun or more each day. Plant it near patios and entryways or in shrub borders to add color. Hardy hibiscus make excellent flowering hedges or mass plantings for a tropical-looking touch to your garden. It combines well with other perennials such as daylilies and Russian sage. Hardy hibiscus looks great with ornamental grasses, such as feather reed grass 'Karl Foerster.' It also makes a good container plant if kept well watered and fed.
The key to good growth and flowering is to keep the soil consistently moist while fertilizing occasionally. For a bushier plant, sow three feet apart and pinch back the growing tips when it is eight inches tall, and again when it's 12 inches tall.
Hardy hibiscus needs very little care over the winter. Its roots are hardy to zone 4 with no protection. They die to the ground each year and the new spring growth rises from the roots. After a hard frost in the fall, cut the plant back to four to five inches. The old stem stubs will remind you where they are in the garden. This is important because it is the very last perennial to emerge. Often, they don't show signs of life until late May or early June. Many gardeners assume their hibiscus plant has died over the winter, so they dig up and destroy live plants without giving them a chance to emerge.
Once they start to grow, they grow fast. Some varieties will grow up to eight feet tall. One of the nice features about 'Disco Belle' is that it only grows 24 inches tall, but still produces a constant supply of eight-to 10-inch white, pink or red flowers from mid-summer through fall. They are excellent perennials for smaller gardens. The 'Disco Belle' hibiscus at Reiman Gardens are stunning. A beautiful grouping is planted near the entrance to the Marge Hunziker House at the south end of the Gardens.
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