Institute of Food and Agricultural Sciences
Hendry County Horticulture News
Hibiscus - The Most Popular Florida Shrub
The Chinese hibiscus, (Hibiscus rosa-sinensis L)., is probably the most popular and widely planted shrub in Florida. Although long cultivated in the sunshine state, the hibiscus is believed to be native to China and came to Florida by way of the South Pacific and Hawaii.
Little is known about the early history of tropical hibiscus. Early Chinese hibiscus may have been hybrids involving two or more species from areas adjacent to the Indian Ocean. Today, most of the commonly grown varieties in Florida are probably hybrids. A few other hibiscus species such as H. schizopetalus and H. tiliaceus are also seen in south Florida.
Most hibiscus varieties have one-day flowers; the blossoms open early in the morning and wilt late that afternoon. Flowers of a few varieties remain open for two days. Although individual flowers do not last long, the flowering season is nearly all year in our area. Most hibiscus are odorless, but a few varieties are slightly fragrant.
Hibiscus varieties vary widely in plant growth habit and size, the form and color of the flowers, and adaptability to specific environmental conditions. Plants range from low, spreading forms to upright varieties reaching 20 feet in height. Some are compact and dense while others are open and thin.
Tremendous flower variations exist between cultivars. The basic colors are red, range, yellow, white, lavender, and brown. In addition, there is a broad range of color combinations, color shades, and flower forms. Hibiscus breeders have been active in Florida as evidenced by the hundreds of named varieties found today. In general, the older varieties which grow well on their own roots are the most desirable for use in the landscape. Many of the newer varieties grow well only as grafted plants and are not widely available.
Plants may be killed to the ground by 28 to 30°F temperatures, but established plants will normally re-sprout in the spring and bloom on new growth that summer. Hibiscus should be protected from cold northern winds by fences, buildings, screens, or trees.
The amount of sun required for optimal hibiscus growth and flowering differs with variety. Generally, half a day of direct sunlight is the minimum requirement.
A wide range of well-drained soils are suitable for hibiscus. Regular fertilization is essential in maintaining healthy and vigorous plants. Hibiscus bloom best when fertilized lightly and often. Three or four applications per year are satisfactory: 1) early spring, 2) after first growth flush, 3) midsummer, and 4) early winter. The amount of fertilizer per application depends on frequency of fertilization and size of the plants. Rates can range from one-half ounce of 15-5-10 or 15-5-15 fertilizer for a small plant, up to one-half to one pound for a mature plant per application.
A soil pH of 5.5 to 6.5 is preferred. Hibiscus grown on alkaline soils suffer from micro-nutrient deficiencies. Iron and manganese are most often limiting on alkaline soils. Manganese sulfate and iron chelates useful in correcting deficiencies.
Heavy pruning is best done in the early spring - February or March. Light maintenance pruning may be done any time of the year to remove diseased or dead wood, rubbing branches, and weak or droopy growth. Hibiscus blooms are produced on new growth, so blooming is reduced if the plants are pruned heavily during the growing season. Plants can be pruned to maintain a desired size and shape without disrupting blooming by trimming only one-third of the branches at one time.
Hibiscus find use in the landscape as informal hedges or screens, foundation plants, or background for other garden plants. They do not perform well as formal sheared hedges. Use of a single variety in hedges and other mass plantings is usually more effective than a mixture of several varieties. Hibiscus are often planted too close together. A three and one-half to four feet spacing is recommended for a hedge, but four and one-half to five feet is appropriate in garden areas and foundation plantings.
Several types of chewing pests feed on hibiscus leaves, buds, or flowers at one time or another. These include caterpillars, grasshoppers, snails and slugs, beetles, cutworms, and leaf miners. Pests that suck plant juices can also be a problem. These include scale, mealybugs, spider mites, aphids, whiteflies, and thrips.
Common diseases of hibiscus include leaf spot, canker, and mushroom root rot. Canker is a fungus disease which causes twigs and branches to die back and sometimes the entire plant is killed. Reddish-orange fruiting bodies can often be found on diseased bark. Plants infected with mushroom root rot usually wilt suddenly and die a short time later.
Leaf spots are caused by various fungi and bacteria. These diseases may kill affected leaves but are usually little cause for alarm. Specific recommendations for pest and disease control are available at the Hendry County Extension Office. Always read the label before applying a pesticide.
Premature leaf yellowing and flower bud drop is often a problem with hibiscus. Insects, nematodes, and environmental factors such as poor drainage and excessive water, drought, nutritional deficiencies, over fertilization, or abrupt temperature change are often to blame.
Hibiscus are an old-time Florida favorite that can find a place in almost every landscape. Good luck and good gardening.
Gene McAvoy is the horticulture agent with the Hendry County Extension Service. Direct your horticulture questions to PO Box 68, LaBelle, FL 33975, e-mail - email@example.com or phone 863-674-4092 or 863-983-1598. You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle. Office hours are from 8:00 - 5:00.
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