|Carica papaya subsp. var.||Papaya, tree melon, papaw|
Growth Habit: The papaya is a short-lived, fast-growing, woody, large herb to 10 or 12 feet in height. It generally branches only when injured. All parts contain latex. The hollow green or deep purple trunk is straight and cylindrical with prominent leaf scars. Its diameter may be from 2 or 3 inches to over a foot at the base.
Foliage: The leaves emerge directly from the upper part of the stem in a spiral on nearly horizontal petioles 1 to 3-1/2 feet long. The blade, deeply divided into 5 to 9 main segments, varies from 1 to 2 feet in width, and has prominent yellowish ribs and veins. The life of a leaf is 4 to 6 months.
Flowers: The five-petalled flowers are fleshy, waxy and slightly fragrant. Some plants bear only short-stalked female flowers, or bisexual (perfect) flowers also on short stalks, while others may bear only male flowers, clustered on panicles 5 or 6 feet long. Some plants may have both male and female flowers. Others at certain seasons produce short-stalked male flowers, at other times perfect flowers. This change of sex may occur temporarily during high temperatures in midsummer. Male or bisexual plants may change completely to female plants after being beheaded. Certain varieties have a propensity for producing certain types of flowers. For example, the Solo variety has flowers of both sexes 66% of the time, so two out of three plants will produce fruit, even if planted singly. How pollination takes place in papayas is not known with certainty. Wind is probably the main agent, as the pollen is light and abundant, but thrips and moths may assist. Hand pollination is sometimes necessary to get a proper fruit set.
Fruit: There are two types of papayas, Hawaiian and Mexican. The Hawaiian varieties are the papayas commonly found in supermarkets. These pear-shaped fruit generally weigh about 1 pound and have yellow skin when ripe. The flesh is bright orange or pinkish, depending on variety, with small black seeds clustered in the center. Hawaiian papayas are easier to harvest because the plants seldom grow taller than 8 feet. Mexican papayas are much larger the the Hawaiian types and may weigh up to 10 pounds and be more than 15 inches long. The flesh may be yellow, orange or pink. The flavor is less intense than that the Hawaiian papaya but still is delicious and extremely enjoyable. They are slightly easier to grow than Hawaiian papayas. A properly ripened papaya is juicy, sweetish and somewhat like a cantaloupe in flavor, although musky in some types.
Caution should be taken when harvesting, as papaya is known to release a latex fluid when not quite ripe, which can cause irritation and provoke allergic reaction in some people. The papaya fruit and leaves also contains carpaine, an anthelmintic alkaloid which could be dangerous in high doses. Unripe papaya has contraceptive/abortive effects in large amounts.
|Standard Cyclopedia of Horticulture|
Papaya (Fig. 2755). The papaya (Carica Papaya) is a well-known edible fruit which has spread from its original home in America throughout the tropical world, and is a favorite fruit in many regions. In Hawaii it is said to rank next to the banana in popularity ; in nearly all parts of tropical America it is one of the commonest fruits, while early in the seventeenth century it became known in the Orient and is now grown in India, Ceylon, the Malay Archipelago, and many other regions, as well as in tropical Africa and Australia. The name papaya is considered a corruption of the Carib ababai, which in one form or another has been carried around the world; papaia, papeya and papia are some of the various adaptations which are in use. The English name papaw (or pawpaw) is probably derived from the same source, and is widely used ; in the United States it has the disadvantage of confusing this fruit with Asimina triloba, which is well known in the central and southeastern states under the same name. The Portuguese name, current in Brazil, is mamao (the tree mamoeiro), a word probably referring to the mammiform apex of the fruit; in the French colonies it is called papaye (the plant papayer) ; in German colonies papaja and papajabaum, or melonenbaum. Several other names are used in tropical America, notably fruta de bomba in Cuba, lechosa in Porto Rico, melon zapote in parts of Mexico, and tree melon in English-speaking countries.
The papaya — a giant herbaceous plant rather than a tree — grows to a height of 25 or 30 feet, and is often likened to a palm in general appearance, though there is, of course, no botanical relationship. The trunk is commonly unbranched, bearing toward its apex large soft deeply-lobed leaves sometimes 2 feet across, upon stiff hollow petioles 2 feet or more in length. The wood is fleshy, the bark smooth, grayish brown, marked by prominent leaf-scars.
The plant is normally dioecious, and produces its flowers in the uppermost leaf-axils, the staminate ones sessile on pendent racemes 3 feet or more in length, the pistillate ones subsessile and usually solitary or in few- flowered corymbs. The staminate flowers are funnel- shaped, about an inch long, whitish, the corolla five- lobed, with ten stamens in the throat; the pistillate flowers are considerably larger, with five fleshy petals connate toward the base, a large cylindrical or globose superior ovary, and five sessile fan-shaped stigmas.
Beside the typical dioecious form, in which male and female flowers are confined to separate plants, it is not unusual to find various other distributions of the sexes; these have been studied in Hawaii by Higgins and Holt, who describe (Hawaii Agricultural Experiment Station, Bulletin No. 32) a number of different forms, such as the occurrence of staminate flowers with more or less rudimentary stigmas and ovaries which sometimes give rise to small fruits; a hermaphrodite form, which regularly produces perfect flowers and good fruits; and various other combinations of staminate, pistillate and hermaphrodite flowers on the same and different plants. It will thus be seen that the distribution of the sexes in the papaya is very irregular; it has been reported by some authorities, indeed, that severe pruning or injury to the tree sometimes results in a change of sex, but this has been observed only on staminate trees of the dioecious type.
Aside from these variations in the distribution of the sexes, there are marked differences in the size, shape and quality of the fruits produced by different seedlings of the typical dioecious form, and the papayas of certain regions in the tropics are uniformly superior to those of other regions. In Bahia, Brazil, there are two distinct types, one with small nearly spherical fruits not over 6 inches in diameter, and a very superior type called "mamao da India" which produces fruits 18 inches long, cylindrical in form, and of excellent flavor. With the recent discovery of a method of grafting the papaya, which is fully described under Carica (page 663; cf. also Circ. No. 119, Bur. PL Ind., U. S. Dept. Agric. 1913), the propagation of superior seedlings has been made possible. In addition, much can be done to improve the quality of the fruit through the selection of seed, but the number of males which arise is usually much greater than is necessary to furnish pollen for the female trees. Through vegetative propagation, it is possible to eliminate all unnecessary males and propagate only a sufficient number to furnish the required pollen—not more than one in ten.
The fruit is commonly spherical or cylindrical in form, round or obscurely five-angled in transverse section, from 3 up to 20 or more inches in length, sometimes weighing twenty pounds or over. In general character it strongly resembles a melon; the skin is thin, smooth on the exterior, orange-yellow to deep orange in color, while the flesh, which is concolorous with the skin, is from 1 to 2 inches thick, and incloses a large sometimes five-angled cavity, to the walls of which are attached the numerous round wrinkled and blackish seeds, the size of small peas, inclosed by a thin gelatinous aril.
The flavor is rather sweet; with a slight musky twang which is sometimes objectionable to the novice, and which varies greatly in amount; the best types are of a bland agreeable taste which is almost sure to be relished, and which makes the papaya one of the most popular breakfast fruits in many tropical countries. In Brazil the flavor is thought to be improved if the fruit is lightly scored when taken from the tree, and then allowed to stand for a day so that the milky juice may run out. While most commonly used, perhaps, as a breakfast fruit, like the muskmelon in northern countries, the papaya can be prepared in numerous ways. In Brazil it is served as a dessert, sliced, with the addition of a little sugar and whipped cream. As a salad, in combination with lettuce, it is excellent. As a crystallized fruit it is good; but it has not very much character. When green it is sometimes boiled and served as a vegetable, much as summer squash is in the North. It can also be made into pickles, preserves, jellies, pies, and sherbets. When used as a breakfast fruit it is cut in halves longitudinally, and after the seeds are removed, served with the addition of lemon juice, salt and pepper, or sugar, according to taste.
In the tropics, papayas are in season during a large part of the year, and the yield is enormous, single trees bearing in the course of their lifetime a hundred or more of their immense fruits. In Florida the season extends from December to June, with occasional fruits ripening at other times. While considered a rather difficult fruit to ship, especially when fully ripe, papayas have been sent from Hawaii to San Francisco and marketed in the cities of the Pacific coast. According to Higgins and Holt, the best method of shipment is to wrap the fruits separately in paper, then encase them in cylinders of corrugated strawboard, and pack them in single-tier crates. They should be picked when they show the first signs of'ripeness. Refrigeration during the voyage is important.
The fruit of the papaya, as well as all other parts of the plant, contains a milky juice in which an active principle known as papain is present. This enzyme, which was first separated by Peckholt, greatly resembles animal pepsin in its digestive action, and in recent years has become an article of commerce. Aside from its value as a remedy in dyspepsia and kindred ailments, it has very recently been utilized for the clarification of beer. Its digestive action has long been recognized in the tropics, as evidenced by the common practice of the natives, who rub the juice over meat to make it tender. or wrap a fowl in papaya leaves and let it stand overnight before cooking it.
The papaya succeeds best in regions with a warm climate and rich loamy but well-drained soil. In south Florida it appears to prefer the richer hammock soils to those of pine-lands, but may be very successfully grown on the latter with proper fertilizing. On the Florida Keys, the plant has become thoroughly naturalized, and springs up wherever a clearing is made; the seeds being scattered by birds and other agencies. It withstands but little frost, although it is occasionally possible to fruit it toward the northern part of the state when a mild winter allows it to reach its second summer without injury. In California, the papaya has never been very successful, probably because the nights are too cool to mature the fruit perfectly. It has been noticed in the tropics that fruit ripened in cool weather is poor and somewhat squash-like in flavor. The best locations in southern California are the protected foothill regions, where the ground is sloping and the soil well drained, and where the heat during the summer months is more intense than on the seacoast. An old tree at Hollywood, Los Angeles, bore fruit for several years, but finally succumbed to the cold rains of winter, which often cause the plants to rot off at the base, especially if the drainage is the least bit defective.
In Hawaii the papaya is said to succeed on almost any soil, provided it is well drained. As soon as the plants are well started they like plenty of moisture, and are rank feeders. On the shallow soils of south Florida, organic nitrogen should be abundantly supplied. The papaya is easily grown from seed, which in Florida should be planted as early as possible,—preferably in January,—in order to have the plants in fruit by the following winter. If seeds are washed and dried after removal from the fruit, and stored in glass bottles, they will retain their viability for several years. A light sandy loam is a good medium for germination, and the seeds should be sown rather thickly about 1/2 inch deep. They may be potted off when they have made their third leaves, and from pots later set out in the ground. As the stems of young plants are very succulent, care should be taken to avoid damping-off.
For a permanent orchard, the plants should be set not less than 10 feet apart. The papaya is short-lived, and will not usually remain in profitable bearing more than two to four years. That it is of extremely simple culture is proved by the ease with which it becomes naturalized in tropical regions, and the thriftiness of the wild plants.
Two pests have become sufficiently troublesome in south Florida to require attention, one of which, the papaya fruit-fly (Toxotrypana curvicauda), threatened at one time to become serious (Cf. Journ. Agr. Research, ii. 447-453, Knab & Yothers). This insect occurs in several parts of tropical America; the female inserts her eggs into the immature papaya by means of a long ovipositor, and the larvae first feed in the central seed-mass, but later work into the flesh of the fruit, frequently rendering it unfit for human consumption. The only means of control which have been suggested are the destruction of wild plants and infested fruits, and the production of varieties of the papaya with very thick flesh, so that the female will be unable to reach the seed cavity with her ovipositor;—the young larvae are unable to live in the flesh. A fungous disease, known as papaya leaf-spot (Pucciniopsis caricae) frequently attacks the foliage during the winter season, forming small black masses on the under surfaces of the leaves. It is not very destructive, and easily controlled by spraying with bordeaux mixture.
Adaptation: Papayas have exacting climate requirements for vigorous growth and fruit production. They must have warmth throughout the year and will be damaged by light frosts. Brief exposure to 32° F is damaging and prolonged cold without overhead sprinkling will kill the plants. Cold, wet soil is almost always lethal. Cool temperatures will also alter fruit flavor. Papayas make excellent container and greenhouse specimens where soil moisture and temperature can be moderated.
Location: Papayas like to be warm with both sunshine and reflected heat, so the hottest place against the house where nothing else seems happy is an ideal location. They also like to be as free from wind as possible, although this is not as critical as their need for sun. Papayas can be grown successfully in shade, but the fruit is rarely sweet. They are best planted in mounds or against the foundation of a building where water can be controlled.
Soils: Papayas need a light, well-drained soil. They are easily killed by excess moisture. The soil needs to be moist in hot weather and dry in cold weather. Since this is the opposite of California's rain pattern, in addition to good drainage, plastic coverings to prevent over-wetting in winter may also be worthwhile. Papayas do not tolerate salty water or soil.
Irrigation: Watering is the most critical aspect in raising papayas. The plants should be kept on to the dry side to avoid root rot, but also need enough water to support their large leaves. In winter the plant prefers to remain as dry as possible. A plant that has been injured by frost is particularly susceptible to root rot.
Fertilization: The fast-growing papaya requires regular applications of nitrogen fertilizers but the exact rates have not been established. Feed monthly and adjust according to the plant's response. They can take fairly hot organic fertilizing such as chicken manure if used with deep irrigation after warm weather has started. Phosphorus deficiency casuses dark green foliage with a reddish-purple discoloration of leaf veins and stalks.
Pruning: Papayas do not need to be pruned, but some growers pinch the seedlings or cut back established plants to encourage multiple trunks.
Frost Protection: Papayas need warmth and a frost-free environment, but can often withstand light freezes with some kind of overhead protection. This can be provided by building a frame around the plants and covering it with bedding, plastic sheeting, etc. when frost threatens. Electric light bulbs can also be used for added warmth. Potted specimens can be moved to a frost-secure area. Prolonged cold, even if it does not freeze, may adversely affect the plants and the fruit. Mexican papayas are more hardy than Hawaiian varieties.
Harvest: Papayas are ready to harvest when most of the skin is yellow-green. After several days of ripening at room temperature, they will be almost fully yellow and slightly soft to the touch. Dark green fruit will not ripen properly off the tree, even though it may turn yellow on the outside. Mature fruit can be stored at 45° F for about 3 weeks. Papayas are often sliced and eaten by themselves or served with a myriad of other foods. They can also be cooked to make chutney or various desserts. Green papayas should not be eaten raw because of the latex they contain, although they are frequently boiled and eaten as a vegetable. In the West Indies, young leaves are cooked and eaten like spinach. In India, seeds are sometimes used as an adulterant in whole black pepper.
Papayas are normally propagated by seed. To start a plant, extract the seeds from ripe papayas and wash them to remove the gelatinous covering. They are then dried, dusted with a fungicide and planted as soon as possible (the seeds loose their viability rapidly in storage). Plant the seeds in warm (80° F), sterile potting mix. Seeds should be planted in sterile soil as young papaya seedlings have a high mortality rate from damping off. Potting soil can be sterilized by mixing 50-50 with vermiculite and placing in an oven at 200° F for one hour. Under ideal conditions the seeds may germinate in about two weeks, but may take three to five weeks. Gibberellic acid can be used to speed up germination in some seasons. Seedlings usually begin flowering 9 - 12 months after they germinate.
Seedling papayas do not transplant well. Plant them in large containers so the seedlings will have to be transplanted only once, when they go into the ground. Transplant carefully, making sure not to damage the root ball. To prevent damping off, drench the potting mix with a fungicide containing benomyl or captan. Set the plants a little high to allow for settling. A plastic mulch will help keep the soil warm and dry in wet winter areas, but remove it as soon as the weather becomes warm. Plant at least three or four plants to insure yourself of having females or plant hermaphroditic plants.
Papaya plants can also be grown from cuttings, which should be hardened off for a few days and then propped up with the tip touching moist, fertile soil until roots form. Semihardwood cuttings planted during the summer root rapidly and should fruit the following year.
Pests and diseases
The papaya fruit is susceptible to the Papaya Fruit Fly. This wasp-like fly lays its eggs in young fruit.
Thrips, mites and white flies as well as In red spider and fruit spotting bugs are potential problems in some areas. The plants may also be attacked by mildew, anthracnose, root rot and various virus diseases Fruit flies often ruin the fruit in Florida and Hawaii. Nematodes can attack the roots and are often a factor in the decline of individual plant. Gopher damage can be avoided by planting in wire baskets. Papaya plants should probably be replaced every 4 years or so.
- Kamiya - A selection from Waimanalo. Solo type. Small to medium-sized fruit. Distinct, blocky shape, very short neck. Deep yellow-orange skin and flesh, firm, juicy, very sweet. Dwarf, high-yielding plant. Fairly recent release from the University of Hawaii.
- Mexican Red - A rose-fleshed papaya that is lighter in flavor than Mexican Yellow. Medium to very large fruit. Generally not as sweet as Hawaiian types
- Mexican Yellow - A very sweet and flavorful, yellow-fleshed papaya. Medium to large fruit, can grow up to 10 pounds. Generally not as sweet as Hawaiian types.
- Solo - Fruit round and shallowly furrowed in female plants, pear-shaped in bisexual plants. Weight 1.1 to 2.2 pounds. Skin smooth, flesh firm, reddish-orange, very sweet, of excellent quality. Produces no male plants, only bisexual and female in a 2 to 1 ratio. Introduced into Hawaii from Barbados in 1911. Named Solo in 1919.
- Sunrise (Sunrise Solo) - Pear-shaped fruit with a slight neck. Averages 22 to 26 ounces depending on location. Skin smooth, flesh firm, reddish-orange, sweet, sugar content high. Quality similar to Solo. Seed cavity not as deeply indented as other Solo strains, making seed removal easier. Plant precocious, maturing fruit about 9 months after transplanting, at a height of about 3 feet.
- Sunset (Sunset Solo) - Solo type. Small to medium-sized, pear-shaped fruit. Orange-red skin and flesh. Very sweet. Dwarf, high yielding plant. Originated at the University of Hawaii.
- Vista Solo - Medium to large fruit depending on climate, 5 inches wide, up to 18 inches long. Skin yellow, flesh orange to yellow-orange. Hardy, compact Solo type producing high quality fruit. Needs fairly hot weather to develop sweetness. Self-fertile. Originated in Vista, Calif. by Ralph Corwin.
- Waimanalo (Waimanalo Solo, X-77) - Fruit round with a short neck, average weight 16 to 39 ounces. Skin smooth, and glossy, cavity star-shaped. Flesh thick, firm, orange-yellow in color, flavor and quality high, keeps well. Recommended for fresh market and processing. Fruits of female plants rough in appearance. Average height to the first flower is 32 inches.
- Maxwell, Lewis S. and Betty M. Maxwell. Florida Fruit. Lewis S. Maxwell, Publisher. 1984. pp. 21..
- Morton, Julia F. Fruits of Warm Climates. Creative Resources Systems, Inc. 1987. pp. 336-346.
- Ortho Books. All About Citrus and Subtropical Fruits. Chevron Chemical Co. 1985. pp. 64-66.
- Popenoe, Wilson. Manual of Tropical and Subtropical Fruits. Hafner Press. 1974. Facsimile of the 1920 edition. pp. 225-240.
- Samson, J. A. Tropical Fruits. 2nd ed. Longman Scientific and Technical. 1986. pp. 256-269.