How would you like to have a beautiful, low-maintenance hedge that produces delicious fruit year-round growing in your landscape? We have such a plant and it is quite common in many areas of the state. The shrub I am referring to is the carissa, or natal plum, which is native to South Africa.
The waxy, dark-green foliage appeals to almost everyone, and in addition to the beautiful foliage, carissa produces abundant quantities of attractive white, star-shaped flowers with a jasmine-like fragrance.
Along our coastal areas, carissa has been used for a hedge since it is highly salt-tolerant and can be planted in exposed locations with little chance of being damaged. One disadvantage is the shrub's large spines which are forked at the end, sometimes exceeding two inches in length. Because of its spiny nature, carissa has long been used as a privacy hedge or people-stopper, since an attempt to penetrate a hedge of carissa is rare. It should not be used in areas where small children frequent. While most people use carissa as clipped hedges forming a dense screen, it is not uncommon for it to attain a height of 20 feet at maturity.
Throughout the year the shrub produces large, red, plum-shaped or oval fruits which can be from one to two and half inches in diameter. Each fruit contains very soft, pinkish flesh with a number of small seeds, and has an agreeable flavor. While the fruit is eaten fresh most of the time, it is often made into excellent jelly and a good quality syrup.
Normally carissa is propagated by cuttings by commercial nurserymen, or larger limbs can be air-layered. Propagation by seed is possible, but if they are being raised for the fruit quality, seedlings generally will not come true-to-type, and a variation in the fruit size as well as heaviness of bearing could occur. Usually it is a better idea to attempt propagating by cuttings or air-layering the larger fruiting selections which you may encounter. This way you can be assured of having the particular size and flavor of fruit that you desire. Plants can be kept pruned to whatever size and shape you desire and still produce acceptable quantities of fruit. While carissa grows quite well on all of our Florida soils, the highly alkaline soils of extreme south Florida must be fertilized more frequently with various trace elements to keep them growing well. In most sandy soils a general purpose commercial fertilizer such as a 6-6-6 would be adequate for good growth and optimum fruit production.
Young carissa plants are sensitive to cold and they should be protected from temperatures below 29°F. Once older plants have attained several feet in height, they become cold-hardy and take temperatures of 25°F without being killed.
Carissa prefer sunny locations and well-drained soils. When planted in shade, they may become leggy and produce undesirably. They are not tolerant of flooded conditions and will drown if they are kept submerged for more than a few days. Many dwarfed forms of carissa have very tiny spines and few of them produce much fruit. If you are raising them for the fruit, they certainly would not be as well suited as the large Carissa grandiflora. These smaller varieties have very dense foliage and make a more compact hedge.
A vining carissa, called Carissa karanda, produces a very excellent quality, small, black fruit about one-half-inch in diameter. The fruit can be used as you would the natal plum, and the plant is well adapted for growing on a fence or up into a large tree. The karanda is somewhat more cold tolerant than other carissas and is not as widely available in south Florida nurseries. It is commonly propagated by seed or cuttings, and some of the fruit produced by the karanda is considered of better flavor than many of the natal plum carissas.
Carissa, usually found in nurseries around the state, are recommended as attractive shrubs used in anyone's landscape. They are relatively free of most insect problems and one would rarely need to apply pesticides. The only problem one might encounter is a few types of fungus diseases, particularly on the dwarfed types of carissa, and generally these diseases can be controlled readily by sprays of Copper, Maneb, or Dithane fungicides. Many people tend to overwater carissas, but unfortunately they like to be kept relatively dry and should not be watered more than every week to ten days. Since many people have a lawn sprinkling system that comes on several times a week, this generally will, over a period of time, create problems with growing carissas in their landscape unless they have an extremely well-drained soil.
DATE: January 1985
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