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4 CARISSA Carissa (Carissa macrocarpa) produces masses of beautifully shiny fruits that look something like plums. Their thin red skin covers a pinkish- red, almost mealy, flesh flecked with a milky juice. Flavor varies from tart to almost sweet, depending upon variety and maturity. In South Africa these are already significant commercial resources. Every January and February in southern Natal, for instance, large quantities are sold, notably along the roadsides.1 Prized by one and all, they are bought in considerable quantity in cities such as Durban. Even though production is now haphazard and essentially unsupported by modern horticulture, carissa has good potential as a greater crop. This fruit has an ample edible portion and no stone in the center. It can be eaten whole. Some have a sweet flavor suggestive of raspberry, but most are more like cranberry. These are versatile foodstuffs. Fresh, they can be eaten out of hand. Halved, they make attractive and tasty additions to salads and desserts. The red pulp looks and tastes so good it is often added to sick-people’s foods to entice them into eating bland pasty-colored porridges. The fruits are also dropped into water bottles and gourds to liven up the liquid contents (not necessarily plain water). Despite widespread use as fresh fruits, carissas are more satisfactory when cooked. They are commonly tossed into soups and stews and squeezed over fish and meat, to which they impart both sweetness and flavor. Many are boiled into brightly colored preserves or fruity-flavored syrups. Some are canned or stewed or baked into pies and tarts. The boiled juice and pulp have a milky-red appearance but both turn bright red on the addition of a little sugar. Carissa jelly, made by straining or sieving the stewed slightly under-ripe fruits and cooking them with sugar, is considered among the finest in South Africa. It is now gaining aficionados in 1 In reality, two closely related species occur in South Africa. This chapter focuses on the larger-fruited one, Carissa macrocarpa, which is locally called big num-num (grootnoem-noem in Afrikaans). It is indigenous not only to Kwa-Zulu/Natal but also to the Eastern Cape. Outside South Africa, the fruits are commonly called Natal plum, carissa, or carissa plum. 77

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LOST CROPS OF AFRICA 78 Strictly speaking, the carissa is not an orchard crop—at least not yet. However, it is one of the better-known indigenous horticultural species of South Africa—grown mainly for its hedges, but renowned for its fruits. Not only is a carissa hedge striking to look at and impenetrable, its flowers exude a fragrance as delightful as jasmine, and its shiny red fruits are always in demand. (Forest & Kim Starr, USGS) California and Florida as well. It has an exquisite color and a delicate flavor. A boiled sauce, whose bite and zing are reminiscent of the cranberry sauce Americans slather over turkey at Thanksgiving, is sometimes prepared; some carissa devotees prefer it. In spite of their culinary attractions and widespread use, the fruits themselves are not currently produced in intensive culture. Instead, they are obtained from scattered ornamentals and hedgerows, both of which are common across southern Africa. This is because various types of the bush are used for property boundaries, screens, ground covers, landscaping accents, barriers against intruders (two legged and four legged), or container plants. Carissa is also espaliered against a sunny wall or pruned into small trees to beautify a backyard. Few plants are more decorative, tough, or versatile. The clean and shiny look of the stiff, bottle green leaves makes the shrubs handsome year-round, and the bursts of fragrant flowers and crimson fruits lend added beauty. The star-like flowers, brilliant white against the deep-green foliage, provide special interest during the long flowering season. For this reason, the carissa has become a valued ornamental in California. Hedges of it are to be seen, for example, at the Los Angeles International Airport and at the University of California Santa Barbara.

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CARISSA 79 PROSPECTS We are far from being the first to suggest that carissa be cultivated on larger and wider scale. So far, however, little along those lines has occurred in practice. Nevertheless, recent decades have seen some progress. In that time, types with large fruit and high yields have been selected, and techniques for their vegetative propagation worked out. Some of these elite plants yield fruits as big as oranges.2 A few have been selected specifically because they hold their fruits high above the thorny foliage, making them easier to harvest. And in California, some creeping cultivars have been selected for groundcover. With these (and future) horticultural developments the carissa could become an important fruit of the warmer parts of the world. The species seems poised for greater success, and a handful of horticulturists could set it on its way to culinary usefulness in at least a dozen nations within Africa and without. The benefits of this breakout would go far beyond good nutrition and beautification. The potential for profit may be judged from recent commercial experiences with the cranberry, which in the past few decades has become a billion-dollar resource grown on a mere 10,000 hectares. On its merits, the carissa seems to have a similar potential for producing a terrific return from a tiny area. This is not to say that the task will be easy. Difficulties include problems with picking the fruits (because of the plant’s spines), handling the fruits (sticky milky juice), and preserving the fruits (chilling and handling and dealing with the milky latex juice have yet to be perfected). Nonetheless, relatively modest research seems likely to counteract each of these problems and thereby provide the world a new and especially brilliant crop. Within Africa The carissa plant is quite adaptable. It grows especially well in subtropical coastal areas—such as in Natal, southern Florida and Southern California—where it has a competitive advantage over plants that are bothered by sand and sea and ocean spray. But it appears to be adapted to other types of locations, although just how well it will perform as an economic crop is presently far from certain. 2 Carissas with diameters of 6 cm have been produced in California. Information from C.A. Schroeder.

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LOST CROPS OF AFRICA 80 Humid Areas The promise in Africa’s humid lowlands is uncertain and could be slight. The climatic ranges of Africa’s various Carissa species are currently undetermined, but the plants tend to occur in subtropical and warm-temperate zones. Dry Areas The species highlighted in this chapter (Carissa macrocarpa) enjoys its greatest production (at least given current experience) not in dry regions but in well-watered subtropical and warm-temperate zones. It has, however, quite reasonable, although not exceptional, drought tolerance.3 On the other hand, a related species, Carissa haematocarpa, withstands desiccated sites well, and holds high promise as a dryland crop. Upland Areas Only trials will tell whether the carissa will prove a useful crop for Africa’s highlands. For that particular region, Carissa bispinosa would likely be a better choice. Indeed, this relative might become strikingly useful throughout many tropical highlands. In its utilitarian promise it is almost as good as Carissa macrocarpa. Beyond Africa On the face of it, this is a plant with appeal beyond Africa. It is already cultivated (mainly as a hedged ornamental) in many subtropical areas around the world, as well as in a few tropical locations. But it is possible carissa will become a “cranberry for the warmer regions.” Whether (or how soon) this happens will depend more on personal initiative than scientific support or government grant. Although the plant is already sufficiently developed for use as a crop, dedicated individual attention is needed to make it a satisfying commercial success. USES Like many species highlighted here, carissa offers many uses, including: Fresh Fruits In South Africa, most carissas are eaten out of hand. For this, they must be fully ripe, dark red, and slightly soft to the touch. Like a strawberry, they can then be eaten whole, without peeling or seeding (this fruit’s most outstanding feature) and have only slight acidity. Halved or quartered, ripe carissas make particularly good toppings for cakes, puddings, and ice cream. They are also much praised in fruit salads, to which they add both sprightly tang and vivid color. 3 Information from Harry van den Burg.

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CARISSA 81 CARISSA HEDGES The carissa is particularly valued as a hedge plant. It is used extensively in the southern half of the United States as an ornamental shrub and hedge planting. It withstands shearing admirably and its growth is compact and low. “To make a hedge,” wrote David Fairchild, the dean of US plant explorers, “is a very simple matter. The seeds are sown in a seedbed, and when the young plants are 15 cm high they are transplanted to the place chosen for the hedge and set a foot apart, alternately in parallel rows, distant from one another a foot or more. As the plants grow they are trimmed into the desired hedge form, and the oftener they are trimmed the thicker they interweave their tough, thorny branches, making an impenetrable barrier for stock of all kinds. When in flower the white jasmine-like blossoms show off strikingly against the dark background of foliage; and the red fruit which follows is quite as pretty.” Processed Products This is the carissa’s most immediate market. It may be processed into canned or frozen fruit, jelly or preserves, salads, sherbets, and sauces as well as juice. When less than fully ripe, they are very acid. Indeed, they can be considered a sort of “Africanberry,” yielding tangy sauces and jellies resembling those North Americans enjoy with turkey. As noted, unripe carissas are also good for jelly and jam, pies, and tarts.4 They are preserved whole by pricking, cooking briefly in a syrup, and sterilizing in jars. Peeled or unpeeled, they are also made into syrup or sweet pickles. Manufacturers of jams, jellies, and other foodstuffs can add a small proportion of ripe carissas to enhance the red color. Fruity vinegars are produced from overripe carissas. Even carissa wine is a possibility.5 Hedges Because of the strong spines, this plant makes great barriers. As has been mentioned, it is particularly valued for this in South Africa. It is especially useful for landscaping and privacy screens near the ocean because it tolerates both salt spray and wind damage. It also makes a sturdy, protective, stock-proof hedge for farms and homes. Even when closely trimmed, it continues yielding fruit in abundance, and home hedges are a major source of the fruits now sold. Prostrate cultivars that hug the soil are widely employed in California as groundcover. 4 At this point in the draft one of our contributors enthusiastically scrawled: “Good jelly with venison!” 5 One contributor attests to that fact. “I’ve tasted some very nice amateur wine from it,” he wrote on an early draft.

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LOST CROPS OF AFRICA 82 The pulp is sweet and milky red. It provides an excellent quantity of vitamin C. (Cori Ham) NUTRITION The carissa has relatively large quantities of sugar as well as sufficient acid and pectin to make good jelly. It is an excellent source of vitamin C, containing somewhat more than in the average orange.6 However, it is only a fair source of the other vitamins investigated. The fruit also contains calcium, phosphorus, and magnesium. HORTICULTURE This plant is easy to grow. Seeds germinate in 2 to 4 weeks but the seedlings grow very slowly at first. Plants grown from seed may begin producing fruit within 2 years,7 but they are highly variable and some prove unreliable and sparse bearers. Vegetative propagation is preferred. Air-layering, ground-layering, or shield-budding are all possible. Cuttings planted directly after removal from 6 One analysis found 53 mg per 100 g of whole fruit. Wehmeyer, A. S. 1986. Edible wild plants of southern Africa: data on nutrient contents of over 300 species. Council for Scientific and Industrial Research, Pretoria. 7 Contributor Cori Ham notes, “I have a record of a carissa seedling bearing fruit just 18 months after germination.”

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CARISSA 83 the parent bush do not readily form roots unless grown over bottom heat. However, a method has been devised whereby nearly cutting grows.8 This consists in notching young branchlets by cutting them about halfway through. These are then bent downward and allowed to hang limply. After two months, when a callus has formed over the notch, the cutting is removed from the parent and placed in sand under a lath shade. Within a month it strikes roots. Such cuttings typically begin producing fruit within 2 years.9 Maintaining the plants is simple. A standard, balanced fertilizer for fruit production seems to suffice. Pollination can be a problem. In its homeland, small beetles, hawk moths, and other night-flying insects visit the flowers. Elsewhere, various degrees of unfruitfulness have been attributed to inadequate pollination. Hand pollination is possible. In future, however, all hazards of poor pollination might be avoided by using plants whose floral structure favors a high degree of self-fertilization. Some of those have already been selected. Even when grown solely as a fruit crop, carissa is often pruned into the form of a narrow hedge. This increases accessibility of the fruit, apparently without diminishing yield. As a fruiting bush, the plant requires little pruning beyond cutting it back to restrain exuberant growth. If left uncontrolled the bush becomes too “spready” for easy access to the upper section where the fruits form. As long as not grossly overdone, trimming the plants is beneficial in that it induces more fruiting tips to develop. The plant may also be trained as a vine along a trellis, although this creates a straggling form of growth and seems to produce fewer fruits. HARVESTING AND HANDLING The main fruit production occurs in summer. The productivity is high, and 3 tons per hectare is considered a minimal yield under commercial production in South Africa. When growing conditions are favorable, the plants produce many off-season fruits as well. The ripe fruits must be handled with care. They are thin-skinned, easily bruised, and highly perishable. Like peaches, they ripen at slightly different times, so each must be harvested as it ripens. LIMITATIONS All parts of the plant exude a milky sap when cut or broken. This is not poisonous but it often can mar the fruit’s appearance. As in figs, however, it 8 Information from Edward Simmonds. 9 Cori Ham also noted: “At the University of Stellenbosch, we’ve found that carissa propagates easily from cuttings if we use a commercially available growth hormone called Seradix B number 2. We’ve also found that the cuttings bear fruits after just 6 months in the nursery. They are grown under irrigation and set fruit continuously.

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LOST CROPS OF AFRICA 84 disappears with cooking. Stewing or boiling causes the sap to adhere to the pot (which must not be aluminum) and it can be easily rubbed off with a dry paper towel or a cloth soaked in salad oil.10 The fruits have a short shelf life because the “milk” in the red flesh congeals. This is a concern in discerning markets and where the fruit is unknown. For the same reason, the cooked pulp and juice can turn an ugly, milky red. Adding sugar, however, transforms them into a brilliant and beautiful shiny red treat. The shrub is viciously thorny; to pick the fruit without jabbing yourself is difficult. Moreover, the fruits themselves are often pricked and punctured, which induces decay and blemishes. Carissas are eaten fresh only when fully ripe. They are best if eaten the day they are picked. Under-ripe fruits lack the tangy, raspberry-like flavor and their latex tends to coat the mouth. NEXT STEPS Many things can be done to move the carissa forward into greater use. These include the following: Varietal improvement There is much variation in carissa. In quality the fruits range from soft and many-seeded to firm and almost seedless. Many advances seem possible through selection and breeding. These include: • Creating plants with fewer or shorter spines (to facilitate harvesting); • Developing fruits with longer shelf life; • Improving the fruits’ flavor, appearance, and juiciness; and • Raising the productiveness of the plants; some fruit very prolifically while others fail to set more than a few fruits (despite blooming freely). Plantation trials During the testing phase little genetic development is needed: the selections available are already of adequate (although not ultimate) quality. Tests and trial plots using better clones should be established to study the yield-per-hectare, the management methods, harvest requirements, and other features that have to be done on a practical scale. Horticultural advancement In addition to genetic improvement, yield must also be raised and the regularity of fruiting smoothed out by such things as irrigation, fertilization, pruning, and the inducement of dormancy. In United States, various degrees of unfruitfulness have been attributed to inadequate pollination and the unproductive plants, apparently self-infertile, have been cross-pollination by hand, after which they bear fruits normally. 10 At this point on the manuscript, contributor Cori Ham noted: “The milky latex gave problems in manufacturing nectar. The latex settled out in the bottles into an unattractive white layer and it also stuck to the equipment causing a major cleaning operation.”

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CARISSA 85 As carissa (i.e., C. macrocarpa) grows so well on its own roots, there seems little point in seeking compatible rootstocks. However, Firminger, an English horticulturist who worked in India in the mid-19th century, stated grafting carissa onto seedlings of karanda (a related Asian species, Carissa carandas) rootstock considerably increased fruitfulness and reduced the tree’s size, making it easier to handle and harvest. This needs reconfirming. SPECIES INFORMATION Botanical Name Carissa macrocarpa (Eckl.) A. DC Family Apocynaceae Synonyms Carissa grandiflora (E. Meyer) A. DC; Arduina macrocarpa Eckl.; A. grandiflora E. Mey.; Jasminonerium grandiflorum (E. Mey.) Kuntze. Common Names English: carissa, carissa plum, Natal plum, Ethiopia: agam French: carissa South Africa: amatungulu (Zulu)11, big num-num, grootnoem or grootnoemnoem (Afrikaans), um-tungulu (Xhosa) Uganda: epwakai/oba, acuga, enyonza, omyonza, omweronde Description The carissa is a large shrub or small evergreen tree as much as 6 m tall when left to grow free. It is twiggy, densely branched, and its stems bear long, strong, stiff, bifurcated spines. All parts contain milky latex. The species includes much genetic diversity and types varying greatly in growth habit, cold tolerance, spine shape and form, self-compatibility, and fruit characters have been observed. Plants from seed usually grow into branchy shrubs, though a few become (after many years) attractive small trees with substantial trunks. Those grown from cuttings vary from prostrate ground covers to tall hedge plants. Cuttings tend to sucker badly unless all belowground buds are first removed. Fragrant, white flowers—up to about 5 cm in diameter—appear intermittently all year (especially in warm areas near the coast), but most abundantly in spring and summer. They are big, attractive, and reminiscent of star jasmine. Some gardeners compare their sweet fragrance to jasmine; others to orange blossoms. 11 Amatungulu is a plural; for one fruit the Zulu name is umntungulu.

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LOST CROPS OF AFRICA 86 Some carissa plants bear flowers that are functionally male. These male blossoms are larger than normal, their anthers are larger, and the stamens are much longer than the style. Functionally female flowers have stamens and styles of equal length as well as small anthers that produce no pollen. The fruits appear in summer through fall, but at least a few can usually be found ripening every month of the year. They are paired berries, ovate to spherical, and 2.5 to 5 cm long. A fully ripe fruit has a waxy skin that is bright crimson streaked with darker red; it is thin and bruises easily. The flesh inside is deep red or crimson with white mottling. In the center are about twelve small brown flat seeds. Some are nearly round while others are elongated and pointed at both ends. Distribution The carissa is a common coastal species in South Africa. It is found on sand dunes and on the edges of coastal forest in Eastern Cape Province northwards through Natal to Mozambique. Now widespread tropically, it has become fairly common in southern Florida and is established in cultivation in southern California. Horticultural Varieties Horticulturists in South Africa, California, and Florida have selected and named carissa types that tend to bear more reliably than normal.12 These are now being propagated vegetatively to reproduce them true to form. They tend to have large oval fruits of good texture and few seeds; they mature evenly and have good qualities for making jellies and for pies. They are also very productive. In California, cultivars selected for fruit quality and productivity include Fancy (an erect form bearing many large fruits with few seeds), Torrey Pines (produces good crops of fruit and abundant pollen), Frank (low yielding, but a good supplier of pollen), Chelsey, and Serena. In Florida one of the best fruit bearers is said to be Gifford. Efforts have been directed to the development of dwarf, compact, less spiny types for landscape use. Popular among these are: Bonsai, Boxwood Beauty, Dainty Princess, Grandiflora, Green Carpet, Horizontalis, Minima, Ruby Point, Prostrata, and Tuttle. Environmental Requirements The plant’s climatic limits are basically unknown. However, based on present-day knowledge, it requires a warm, moist subtropical location. It 12 A list is given by Julia Morton in, Morton, J.F. 1987. Fruits of Warm Climates. Julia F. Morton, Miami, Florida.

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CARISSA 87 accepts a variety of exposures including full sun and fairly heavy shade. In shade it tends toward taller growth. Rainfall Although native to coastal areas with annual rainfall of about 1,000 mm, the plant is drought-resistant and requires no watering in summer rainfall areas. As noted earlier, it has reasonable drought tolerance. Altitude Unreported, but in Swaziland, it reaches about 1,000 m. A likely upper limit for good growth is 1,500 m. Low Temperature The carissa grows where temperature rarely falls below freezing. Well-established plants can, however, survive -5°C relatively unscathed. Young plants need protection when the temperature drops to about zero. High Temperature The upper limit is unknown but during summer in Pretoria it survives temperatures up to 32°C (in the shade). Best growth is obtained in full sun. Soil The plants are not exacting in soil requirements. Almost any substrate, limestone heavy clay to sand, is fine as long as it drains well. Salinity Carissa is quite salt tolerant. For irrigation purposes, water of 8 mmho conductivity (about 5,000 ppm) is acceptable. As mentioned, it withstands salty spray, making it a good choice for coastal gardens. Related Species Generally speaking, Carissa species in Africa occur in two vast belts from Senegal to Sudan, and from Ethiopia to South Africa. These, too, produce edible fruits. At this stage, they remain undeveloped and the fruits seem less tasty then the species from Natal. As noted, however, C. haematocarpa may have special potential in drier areas, and C. bispinosa at altitude. A few Carissa species are also found in Europe, Asia, and Australia. Though C. macrocarpa currently seems most promising as a potential cultivated crop, the others deserve exploratory research and testing.