“Tropical Hibiscus” is a term widely used to describe cultivars of Hibiscus rosa-sinensis, a member of the plant family Malvaceae. Also known informally as Chinese Hibiscus or China Rose, hibiscus varieties are widely grown as ornamental flowering plants. Over 10,000 varieties have been created by hybridizing, many of those by amateur garden hobbyists.
Originally native to eastern Asia, Tropical Hibiscus have been spread so widely around the world that exact original locations of the various species are difficult to pin down. In the future, perhaps genetic surveys will make it possible to narrow down the originating locales of these species.
Native to tropical and sub-tropical climates, tropical hibiscus are not frost tolerant, so the plants require extra care and protection to grow in temperate climates. In the United States, tropical hibiscus are common yard plants along the Gulf Coast, treasured by fanciers of their exotic blooms.
In warm climates, some common varieties may grow into quite large shrubs, up to 10 feet or more in height. However, it is more common to find hibiscus grown as garden or foundation plantings, kept pruned to two to four feet in height. Some hybrid varieties have sprawling tendencies, and are sometimes marketed in hanging baskets.
Species type tropical hibiscus plants usually produce flowers with 5 petals, generally in shades of red or white. Through extensive hybridizing, nearly 10,000 varieties have been produced, with blooms in a wide spectrum of nearly all colors, with the exception of true blue.
A large percentage of all hibiscus rosa sinensis varieties (cultivars) have been produced by hibiscus enthusiasts who grow and hybridize hibiscus as a hobby. The hybridizing process is simple, just take the pollen from one hibiscus flower, and place it on the pads of another hibiscus bloom. Now, wait for the bloom that has been pollinated to naturally close and it may produce a seed pod in a week or two. Some hibiscus varieties do not produce seed as readily as others, especially certain exotic hibiscus plants that are the result of generations of hybridizing. Once the seed pods have developed fully, the seeds are planted to produce new cultivars that derive characteristics from both of the parents, as well as preceding generations of hibiscus varieties.
Hybrid flowers sometimes exhibit the shape of the parents, but often develop in another of the incredible variety of other shapes and sizes exhibited by Hibiscus rosa-sinensis cultivars. Some show blooms are nearly 12 inches across, while others have a multitude of tightly clustered petals.
Hibiscus rosa-sinensis does not appear to have the genes necessary to produce a true blue color, although varies hybrids have created semi-blue coloring. Certain surface textures, or sheen, can produce an effect that appears very close to a true Blue color. In recent years, some hybridizers have attempted (and by now may have succeeded) in crossing with other species to introduce the blue color to tropical hibiscus show blooms.
Although some species-type hibiscus do attract hummingbirds, many exotic hybrids have been hybridized by hobbyists for size and appearance, specifically to win hibiscus shows. Most of those hybrid flowers have little or no scent, and may produce very little nectar, so are generally less attractive to the beautiful little birds.
However, tropical hibiscus do attract a number of common garden insect pests. For casual gardeners, this is not usually a major problem. However, collectors intent on producing perfect show quality blooms often have dozens or hundreds of plants, and often spend considerable time and effort controlling pests.
Regardless of their tropical vulnerability to cold weather, millions of Tropical Hibiscus are grown in temperate climates, producing amazing colorful blooms for both gardeners and collectors.
Plants sold in local garden centers generally fit within the following guidelines:
Size: Potted hibiscus are commonly 2 to 4 feet high and across. Some in-ground hibiscus varieties may grow much larger, up to 10 feet or more in warm climates.
Soil & Planting: Hibiscus like loose, well drained soil with lots of organic matter. Soil should be kept very slightly damp. Tropical hibiscus will develop root rot and die if they sit in soggy soil. In clay soils, raised beds will often improve growth and longevity. Mulch to conserve moisure and protect roots from heat. Plants in pots should be watered often, but do not let water sit in trays under pots.
Watering: Water often and lightly. Do not drown the plant! Drip irrigation is great for hibiscus, as it is easy to regulate, and also avoids getting water dropleds on the delicate flower petals.
Spacing: Plants should be spaced with room between, to let air circulate around the plants, and to prevent insects and other pests from spreading easily from plant-to-plant.
Sun: Hibiscus like lots of sun, but not lots of heat. Placement to provide morning sun will promote growth and blooming, but in very hot climates some shade or partial shade at mid-day may protect the plant and benefit blooming. Partial sun all day is ok for most varieties. Some varieties that are not blooming well may respond positively to moving to another area of the yard, with a different micro-climate.
Temperature: Tropical hibiscus are not “hardy”, and will die if they freeze. If a plant is heavily mulched, roots may survive a light freeze, but if the plant dies back to the graft, next season’s growth may be the root stock plant, not the fancy variety that was previously blooming there! Many growers keep their plants in pots, so that they can be brought indoors during freezing weather. Most serious hibiscus collectors/fanatics have some sort of greenhouse, either makeshift or permanent. Hibiscus kept warm in a greenhouse will continue to produce beautiful blooms year-round!