Carica papaya



Carica papaya

L. 1753

pronounced: KAIR-ick-uh puh-PIE-uh

(Caricaceae — the papaya family)


common names: pawpaw, papaya

Before we say too much about the pawpaw tree, we should remember that it is not a tree, but a large herb, and that most of the world, when it talks about a ‘pawpaw’, means the fruit from an entirely different species Asimina, which is a member of the Annonaceae family, and not related to what we call a pawpaw in Australia. Our fruit is more properly called papaya, although the custom seems to be arising in Australia of calling the yellow-fleshed fruit (usually produced from monosexual flowers) pawpaw, and the pink-fleshed fruit (from bisexual flowers) papaya.

Carica comes from the Latin carica, a kind of dry fig, and used because of the similarity of papaya leaves to fig leaves. Papaya is probably from a Caribbean name for the plant.

It is not known exactly where the papaya originated, but it is believed to be native to somewhere in Central America. It is known that seeds were taken to Panama, and from there to Dominica, before 1525, and that cultivation had spread to warm elevations throughout South and Central America, southern Mexico, the West Indies and the Bahamas, and to Bermuda by 1616. Spaniards carried seeds to the Philippines in about 1550, and the papaya travelled from there to Malacca and India. Seeds were sent from India to Naples in 1626. Now it is familiar in nearly all tropical areas of the world.

The pawpaw is a large tree-like plant, the single stem growing from 5 to 10 m tall, with spirally arranged leaves at the top of the trunk. Scars can be seen on the lower trunk where leaves and fruit have been previously borne.

The leaves are large (up to 70 cm in diameter), deeply palmately lobed with 7 lobes. The plant is usually unbranched unless it has been lopped.

In nature, pawpaws are dioecious, i.e., having male and female flowers on different trees. The male flowers have a rudimentary non-functional ovary, but no stigmas. Commercial cultivars tend to be gynodioecious, i.e., dioecious, but having bisexual flowers on some plants and only female flowers on other plants of the same species; but there are also monoecious plants, having both male and female flowers on the same plant. Also, some produce flowers that are not of these basic forms, but exhibit different degrees of maleness and femaleness. This tendency to change in sexual expression seems to be triggered by climatic factors, such as drought and variable temperatures. The tendency to produce male flowers seems to increase at high temperatures.

The flowers are very similar to those of the frangipani, but are much smaller and wax-like. They appear on the axils of the leaves. The yellow fruit comes from dioecious trees, and the male inflorescences are usually on long stalks. On the female trees, the fruits that develop are large, up to about 45 cm long by 20 cm in diameter. As the fruit ripens, the skin turns yellow, and here the fruit must be picked as soon as the first tinge of yellow skin appears, or it is lost to either possums or fruit bats.

Fruit production may occur through cross-pollination, self-pollination, or parthenocarpy, a form of asexual production from the female flower, without any pollination. In the last case, the fruits will be seedless, or at least contain no viable seeds. The shape of the fruit depends on the sex of the flowers: female flowers will produce spherical to ovoid fruit; bisexual elongata, with self-pollinating perfect flowers, with 10 anthers arranged in two sets, will produce cylindrical to pear-shaped flowers; bisexual pentandria (whose flowers look like a female flower, but when taken apart 5 anthers appear) will produce fruit that is ovoid and lobed; and bisexual intermedia (a type between the elongata and pentandra) will produce carpelodic (cat face) fruit.

I have recently been shown some plants that in their first year’s fruiting produced normal pawpaws from bisexual flowers. The trees having been cut back for their second year’s fruiting (as is often done to ease the picking of the fruit), the new season’s fruit has grown on stalks, rather than close in to the leaf axils as is usually the case. There are several ways in which this might happen. Pawpaw has a highly complex capability in sexual expression. Some plants bear only short-stalked pistillate (female) flowers, or short-stalked bisexual flowers, while others may bear only staminate (male) flowers, clustered on long panicles; but there are also monoecious plants having both male and female flowers. Pistillate trees tend to be stable, while staminate and bisexual trees may be ‘ambivalent’, going through seasonal sex reversals. There is quite a range of possible variation, and the proportion and type of flowers may vary even on the same tree. The trees pictured, with their fruits on longer-than-usual stalks, must have produced either some bisexual or some female flowers on pedicels rather than in the leaf axils. It will be interesting to see and taste them as they ripen.

The fruit is usually eaten raw, minus skin and seeds. The unripe fruit can be eaten cooked, and is used extensively in Thai cuisine. The black seeds are edible and have a sharp, spicy taste. They are sometimes dried and ground up to be used as a substitute for black pepper. In some parts of Asia the young leaves of the plant are steamed and eaten like spinach. Eating too much pawpaw can, like the eating of too many carrots, cause carotenemia, which causes the palms of the hands and the soles of the feet to turn yellow, but is otherwise fairly harmless, except that it may be misdiagnosed as jaundice. Both the green fruit and the plant’s latex are rich in an enzyme called papain that is useful in tenderizing meat, and this has been used by indigenous Americans for thousands of years. The enzyme is used as a component of powdered meat tenderizers. It is also used in the treatment of cuts, rashes, stings and burns.

The caterpillar of the Yellow Peach Moth Conogethes punctiferalis uses the plant as a food source.

Those of a scientific bent may be interested to learn that the pawpaw was the first fruit ‘tree’ to have its genome deciphered.




Photographs taken in Picnic Bay 2008-2013 and Nelly Bay 2013
Page last updated 30th October 2018