Hibiscus can be a show-stopper in any garden, with flowers that can be as large as 12 inches in diameter. The mild climate of the Tampa Bay area is ideal for this tropical plant. Here are some tips on growing the colorful blooms in your yard.
Good drainage is important. Make sure hibiscus doesn't stay wet, but avoid drying it out especially in the hot weather. Add organic matter and mulch to keep the soil moist.
The plant likes lots of light, but too much direct sun when it's hottest may lead to reduced blooms. Try planting where it get some shade midday for plentiful and larger blooms.
A sandy soil rich in organic matter that will retain water is best. Mulching retains moisture and shields the roots from the hot sun. For potted plants, some growers like to use a commercial soilless mixture and others prefer a mixture that contains sand, pine bark, topsoil and compost. A best soil pH is 6 to 7.
Prune the plants to shape and manage size, invigorate old plants, and get rid of diseased and dead wood. Prune after the freezes are over with so new growth won't get damaged. Prune a third to a half of the plant. Use sharp shears and prune just above an "eye."
Hibiscus is a heavy feeder, so fertilize lightly and often. Use fertilizers that include trace elements, like iron, copper and boron. Growers prefer low phosphate dry fertilizer, such as 7-2-7 to produce better quality blooms. Water soluble fertilizers can be used for foliar feeding (spraying on leaves) and for potted plants. A slightly acidic soil (pH of 6 to 7) helps the plants absorb nutrients.
If left on the plant or cut and brought inside (no water necessary), the blooms of most varieties last only a day. There are a few that will still look good after two or three days.
Some of the garden varieties may grow to heights of 10 to 15 feet or more. Most of the hybrids won't get nearly that large, in fact, some may only grow a few inches a year.
Control aphids, thrips, whiteflies and spider mites. Water the plant thoroughly before using insecticides to lessen the shock. It's best to apply in the early morning or in the evening when temperatures are below 80 degrees. Apply to both top and underside of the leaves. For most insect problems, use systemic Orthene, or Cygon which is often used against scale and other insects. Whiteflies can be controlled with products containing imidacloprid, as well as with soaps and oil, such as Ultra Fine Oil. Some growers use neem products, WD40 or cooking spray on stems and branches to control scale.
Occasionally, bacterial and viral diseases may threaten a plant. Try to avoid spreading these problems by sterilizing shears and isolating the affected plant if possible. Plants that cannot be revived should be carefully discarded. Try to consult an expert. Many diseases can be cured with the proper treatment. Sometimes something as simple as adding a weak chlorine bleach solution to the soil may kill the pathogen and sometimes a specialized product is necessary. Remember to properly water and fertilize the plant to better resist problems.
Tropical hibiscus can withstand freezing temperatures for a brief time before there's damage. Cover your outdoor plants when there's a freeze warning to trap ground heat. For potted plants, bring them inside. Freeze-damaged plants should be cut back to living wood after the danger of freezing has passed or when growth resumes.
Pots or in ground?
Many growers prefer pots because if a plant isn't thriving in one area it can be moved to a different location where it might do better. Also, applications of nutrients are slower to leave the root area if the plants are in pots. There's less risk of nematodes, too. But make sure the pots drain well. Plants in the ground benefit from being able to spread their roots farther and will need less frequent watering.