The papaya, Carica papaya L., is a member of the small family Caricaceae allied to the Passifloraceae. As a dual- or multi-purpose, early-bearing, space-conserving, herbaceous crop, it is widely acclaimed, despite its susceptibility to natural enemies.

In some parts of the world, especially Australia and some islands of the West Indies, it is known as papaw, or pawpaw, names which are better limited to the very different, mainly wild Asimina triloba Dunal, belonging to the Annonaceae. While the name papaya is widely recognized, it has been corrupted to kapaya, kepaya, lapaya or tapaya in southern Asia and the East Indies. In French, it is papaye (the fruit) and papayer (the plant), or sometimes figuier des Iles. Spanish-speaking people employ the names melón zapote, lechosa, payaya (fruit), papayo or papayero (the plant), fruta bomba, mamón or mamona, depending on the country. In Brazil, the usual name is mamao. When first encountered by Europeans it was quite naturally nicknamed "tree melon".

Commonly and erroneously referred to as a "tree", the plant is properly a large herb growing at the rate of 6 to 10 ft (1.8-3 m) the first year and reaching 20 or even 30 ft (6-9 m) in height, with a hollow green or deep-purple stem becoming 12 to 16 in (30-40 cm) or more thick at the base and roughened by leaf scars. The leaves emerge directly from the upper part of the stem in a spiral on nearly horizontal petioles 1 to 3 1/2 ft (30-105 cm) long, hollow, succulent, green or more or less dark purple. The blade, deeply divided into 5 to 9 main segments, each irregularly subdivided, varies from 1 to 2 ft (30-60 cm) in width and has prominent yellowish ribs and veins. The life of a leaf is 4 to 6 months. Both the stem and leaves contain copious white milky latex

The 5-petalled flowers are fleshy, waxy and slightly fragrant. Some plants bear only short-stalked pistillate (female) flowers, waxy and ivory-white; or hermaprodite (perfect) flowers (having female and male organs), ivory-white with bright-yellow anthers and borne on short stalks; while others may bear only staminate (male) flowers, clustered on panicles to 5 or 6 ft (1.5-1.8 m) long. There may even be monoecious plants having both male and female flowers.

Some plants 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. Some "all-male" plants occasionally bear, at the tip of the spray, small flowers with perfect pistils and these produce abnormally slender fruits. Male or hermaphrodite plants may change completely to female plants after being beheaded

Generally, the fruit is melon-like, oval to nearly round, somewhat pyriform, or elongated club-shaped, 6 to 20 in (15-50 cm) long and 4 to 8 in (10-20 cm) thick; weighing up to 20 lbs (9 kg). Semi-wild (naturalized) plants bear miniature fruits 1 to 6 in (2.5-15 cm) long. The skin is waxy and thin but fairly tough. When the fruit is green and hard it is rich in white latex. As it ripens, it becomes light- or deep-yellow externally and the thick wall of succulent flesh becomes aromatic, yellow, orange or various shades of salmon or red.

It is then juicy, sweetish and somewhat like a cantaloupe in flavor; in some types quite musky. Attached lightly to the wall by soft, white, fibrous tissue, are usually numerous small, black, ovoid, corrugated, peppery seeds about 3/16 in (5 mm) long, each coated with a transparent, gelatinous aril.

Trees produce about 50% of their papain yield in the first year, 30% in second year, and 20% in third year. Yields range 70-130 kg/ha. If this represents 5% of the latex, the latex yields are close to one MT/ha/yr. Morton recounts yields of 20-25 kg dried papain per hectare in the first year; 90-100 in year 2, 60-90 in year 3, 30-40 in year 4, and 20 or less in year 5. She equates 1 kg crude papain with 5 kg fresh latex. A tree may bear 30-150 fruits per year, each weighing up to 9 kg. Up to 34,000 kg marketable fruit per ha is a credible yield, but yields of 100 MT fruit are reported (Duke, 1978). Murthy and Natarajan (1982) report that on fertile soils 'Honey Dew' will yield ca 100 MT/ha fruit (with 1750 bearing trees/ha) the first year, 85 the second, and 75 the third. Previously Sri Lanka and presently Uganda and Tanzania are the principal producers of papain. United States is the principal importer of papain, using it mainly for meat tenderizers, beer treatment, chewing gum, and textile and tanning industry. United States imports about 340 tons of crude papain, valued at $2 million. In the tropics the papaya is used for many purposes, and wherever it is grown, is a stable food. Nearly all of Florida crop is used in homes or sold in local markets. Hawaii is the main producer for mainland United States. In 1968, produced 11,775 tons from 830 acres. Many manufactured products are made, especially papaya juice and concentrate.

Origin

The papaya is believed to be native to southern Mexico and neighboring Central America. It is now present in every tropical and subtropical country.

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.

Fruits

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. The fruit (and leaves) contain papain which helps digestion and is used to tenderize meat. The edible seeds have a spicy flavor somewhat reminiscent of black pepper.