Choices, Care And Exotic Varieties
Hibiscus rosa-sinesis (Rose of China) is the tropical hibiscus, the one with large flowers and mind-boggling color choices. It has the longest list of cultivars. You can grow these in a warm climate (zone 9-11) or in containers as annuals or they are small enough to spend the winter indoors. This is the evergreen hibiscus. This is a plant well worth growing and can live over 40 years.
The second main category is Hibiscus moscheutos, the Swamp mallow. This one is hardy in zones 5-9. Here is a quick guide to the differences.
| Name | Hibiscus rosa sinesis (Tropical) | Hibiscus moscheutos (Hardy) |
| Zone | 9-11 | 5-9 |
| Size | usually 8-15′ (taller in tropical areas) 5-8′ w | 3′- 12′(rose of Sharon) |
| Blossom | most var. orange, salmon peach, yellow (not seen in hardy, include double blossoms | white, red, pink, bicolor, no double blossoms |
Tropical Hibiscus-forms shapes and blossoms
Sizes and forms:
There are tree forms, which can be kept small in pots or in the ground. Single trunks and braided trunks are available. Some have different colors braided together. In tropical climates, the trees can grow bigger.
The plant is also available as a shrub that can be grown in the ground, in containers, or used as a hedge or as a privacy barrier. There is a pretty small dwarf variety designed to be used in the house, or a window box. There is a catch, however. They are not true dwarves. The plants are treated with plant growth regulators and after a season the plant will grow taller.
The Flowers
This the feature most people seek out. The flowers come in many sizes, including some quite large, there are singles and doubles. We grow some which appear to be two separate flowers joined together. They come with ruffled edges and centers of other colors. The flowers are trumpet-shaped with dramatic protruding stamens.
The Fancy Exotic Tropical Version
These are small cultivars, they are hybrid crosses with larger, fancier, and more complex flowers than the classic landscape types. You keep them, inside the house or outside for the flower. The colors range from vivid to completely astounding! Some have a metallic appearance.
I wanted to buy one for my mother’s birthday. The grower said you get one wonderful bloom at a time. If it’s ready to bloom and your mom needs to go to the doctor, tell her to take it with her right in her purse. It can bloom in the office. She did and it did!
Growing Conditions
The tropical hibiscus plants will perform best in well-drained soil of slightly acid conditions. It is best grown in full sun except in very warm climates where some afternoon shade can be beneficial. A steady supply of water is important but with good drainage.
In containers, use a potting mix high in organic matter. Keep the same, moist but well-drained environment.
Fertilizer
They require regular fertilizer. They exist to bloom. If feeding weekly they need water-soluble fertilizer -one tsp. per gallon. Hibiscus performs best with frequent, small fertilizer applications. Fertilize when the plant is damp which will protect from fertilizer burn. There are considerable differences in opinions about feeding hibiscus. It does seem important to use high phosphorous for blooms. For example, 5-50-17 is recommended. We use a commercially available product which we can spray on with the water hose.
Pruning
Mature plants can become larger than you need and lose their shape. We love hibiscus for its flowers. But because it blooms only on new growth you will remove your new blossoms.
To maintain blossoms you can prune every 4-6 weeks. Take 2-3 branches from the various sides of the plant. Cut these low and cut just above an outward-facing branch. This will encourage outward growth which will maintain airflow through the plant. This will help the plant to resist disease.
This should allow you a continuous display of flowers while maintaining the health of the plant, Prune hibiscus in spring after the danger of frost has passed and before the summer heat arrives.
Propagation From Trimmings
If you like your hibiscus, don’t throw away the cuttings. Make some more plants for yourself or for gifts. Trim the cutting to about 4″-6″ using only the newly grown material. Remove all but the top 3 leaves. Dip the bottom in rooting hormone and place it in a small pot in well-drained soil.
A mix of potting soil and perlite works well. You can put several root cuttings in one pot. Keep the soil damp not wet until the roots grow -about 8 weeks. At this time you can move the plants to larger pots. Cuttings should be in a place that is warm and humid and not in direct sunlight. Prepare several starter plants, we never expect them “all” to grow. The plants you grow will be duplicates of the parent.
Pests and Disease
Actively growing plants are healthy plants. In the case of hibiscus, this means fed and moist but not wet and in comfortable surroundings. Plants are like us, if we are healthy we have a better chance of resisting disease.
Pests are in categories based on how the pest feeds
Learn as much as you can about Integrated Pest Management
This is a broad-based approach to managing pest damage using the most economical method first to produce the least hazard. It requires regular observation. By daily observation, I can see the first approach of a pest or problem. Often just by removing the pest or damaged leaves, I can solve the problem without using a chemical. If that does not work I might try washing the pest off with water before going to the next level.
Chewing Pests-these are caterpillars and grasshoppers. Remove them as soon as they are spotted. You can do this with your hands.
Sucking Pests- these pierce the surface of the leaf and drink the sap. These include aphids. mealybugs, scale insects, and mites. Mealybugs are important as the residue they leave behind attracts ants. When discovered, remove the initial insects by removing leaves, using hard sprays of water. If an insecticide is needed, start with insecticidal soaps, or horticultural oils. Use products containing acephate. UGA Extension
Disease
Leaf Spot is caused by various strains of fungus. This appears as discoloration, spots on foliage, and possibly leaf dropping. If you can remove the black spots they are most likely pests. Destroy the damaged leaves.
Rot- is caused by a fungus and usually indicates soggy soil. Prepare the site before planting. This includes removing any old root material
Blights- To avoid this keep good airflow (see pruning notes) avoid overhead water.
Virus viruses do appear, from time to time and it seems to be important to use virus-tested stock in plantings. The best way to avoid damage is by keeping healthy plants.
Summary
European explorers found ornamental hibiscus near Chinese temples and palaces. A double red variety was cultivated in London (Chelsea Physic Garden) in 1731. Later travelers noticed that in various parts of the Pacific people identified with the hibiscus in cultural and religious traditions,
Eventually, in Hawaii in the early 20th century the development of new plants really started. The Chinese plants were crossbred with plants from Mozambique, Tanzania, and Kenya. By 1914 a flower show was able to display 400 different offerings. The growth and demand for new and exotic colors and forms has never ended.