A version of this article appeared in the January/February 2010 issue of Serendib, the in-flight magazine of Sri Lankan Airlines.
We have ten jak trees in the garden of our Sri Lankan mountain retreat. Without any contribution from us, the trees maintain a miraculous eco system.
Parrots and hornbills, their harsh cries belying their beautiful appearance, roost in the branches. From time to time, hooligan gangs of langurs swarm in from the jungle to vandalize the fruit and to fight with each other and our dogs. Bushy-tailed rock squirrels busy themselves leaping from tree to tree maintaining several homes to deceive predators. Wild boars come on high-heels in the night to indulge their passion for jak nuts and wreck our fences if we don’t put an adequate supply of nuts outside for them.
The jak tree is a wonder of nature and a boon to humanity as well as other animals. It produces perhaps the largest tree fruits on earth. The tree is extremely versatile.
The botanical name is Artocarpus heterophyllus of the family Moraceae (the amazingly diverse mulberry family). In Sinhala it is called kos; in Tamil pila; in Chinese bo luo mi; nangka in the Philippines and Malaysia; in Thailand, khanun; in Cambodia, khnor; in Laos, mak mi or may mi; in Vietnam, mit.
The jakfruit adapts only to humid tropical climates. It is sensitive to frost in its early life and cannot tolerate drought. It flourishes in rich, deep soil, sometimes on deep gravelly soil. It also does not like “wet feet”. If the roots touch water, the tree will not bear fruit or may die.
In Asia, jakfruits mainly ripen from March to June, April to September. Fruits mature three to eight months from flowering. A good yield is 150 large fruits per tree annually, though some trees bear as many as 250 and a fully mature tree may produce 500.
The tree is large and can grow as tall as 70 feet. The leaves are dark green, elliptic and leathery in appearance with lateral veins with parallel intercostals. The flowers are cauliflerous (developing directly from the trunk) and cylindrical.
The fruit of the tree is large, limey-green to yellow in colour, and bulbous and spiky. The fruit grows in an alarming fashion suspended from the trunk of the tree. If you had never seen one before you might think it was from another planet. The fully-grown jakfruit may be as much as three feet long and can weigh as much as 110 lbs.
The fruit itself has a wide variety of culinary uses. The fleshy part can be boiled or made into a curry or mallun (shredded like cabbage with grated coconut and turmeric and served with rice to counteract spicier dishes).
The flesh when young is called polos. The first time I ate it, the appearance and texture reminded me of tinned tuna fish chunks. Depending on how it is cooked, it can also resemble beef stroganoff. I find it particularly tasty stewed with tomatoes, garlic and lime juice.
Inside the fleshy segments there are oval, whitish seeds (endocarp) or nuts covered by a thin white plasticky membrane (exocarp). These remind me of Brazil nuts. There may be up to 500 nuts in a single fruit. The nuts can be dried, roasted and pounded to make flour, which is blended with wheat flour for baking. They can be included in a curry. The nuts can be fried, roasted, sun-dried (atu kos) to be eaten as a savoury snack. Preserved in brine, or cooked in tomato sauce they can be canned. Sometimes they are preserved in syrup and served as a dessert.
The sweet, fragrant, ripe fruit, varaka, has a flavour somewhat similar to pineapple, but much more subtle and understated and less astringent. This is eaten as a dessert and cleanses the palate like a sorbet after spicy curries.
Tender young fruits may be pickled with or without spices.
Westerners generally will find the jakfruit most acceptable in the full-grown but unripe stage. At this stage, it has no objectionable odour (the odour is not like durian – even when the fruit is rotting on the ground after the monkeys have discarded it, our garden is permeated with a not unpleasant fermenting smell somewhere between vinegar and alcohol) and is cooked like breadfruit or plantain. This stage of the fruit is cut into large chunks for cooking, the only handicap being its copious gummy latex which accumulates on the knife and the hands if one does not use oil as a preventative. It is difficult to clean the sticky gumminess from pans and hobs.
A labourer might breakfast on such a repast and the complex carbohydrates consumed would sustain him for a whole day.
The leaves are used as food wrappers in cooking, and they are also fastened together for use as plates.
I have not tried this myself, but it is said that jakfruit nuts and pulp can cure a hangover. The Chinese find it a cooling and nutritious tonic “useful in overcoming the influence of alcohol on the system.” The seed starch is given to relieve biliousness and the roasted seeds are regarded as aphrodisiac. (I have not conducted a controlled experiment.) Ulcers are treated with the ash of the leaves burned with corn and coconut shells and mixed with coconut oil. Abscesses, snakebite and glandular swellings are treated with dried latex mixed with vinegar. The roots are used for skin diseases, asthma, fever and diarrhea. Heated leaves are placed on wounds and the bark is made into poultices.
In some areas, jakfruit is fed to cattle. The tree is even planted in pastures so that the animals can avail themselves of the fallen fruits. Surplus jakfruit rind is considered a good stock food. The leaves are used as cattle fodder and are thought to be fattening.
The latex serves as birdlime, alone or mixed with Ficus sap and oil from Schleichera trijuga. The heated latex is employed as household cement for mending chinaware and earthenware, and to caulk boats and holes in buckets. It contains which can be used in varnishes.
The hardwood of Artocarpus heterophyllus is used in construction and for making furniture. It is currently quite expensive in Sri Lanka. The grain and texture of jak timber has been likened to mahogany but it is yellow when new. It changes with age to brown or dark-red. It is termite-proof, resistant to fungal and bacterial decay. It seasons easily, and is superior to teak. Jak wood is also used for masts, oars, and musical instruments. Palaces were built of jak wood in Bali and Macassar, and the limited supply was once reserved for temples in Indochina. Roots of old trees are used for carving and picture framing.
The sawdust of jakwood is boiled with alum to make a dye containing the yellow colorant, morin, which is used to color silk and the robes of Buddhist monks.
Sri Lanka is fortunate that this miracle tree grows abundantly just about everywhere in the non-urban areas of the country and even in some city gardens. It makes a major contribution to Sri Lankan life. Because the jak tree is so productive and so useful to the community there are legal restrictions on the felling of the trees and transportation of the wood.
The tree of life – but you wouldn’t want a fruit to land on your head!