The family Bombacaceae is best known for showy flowers and woody or thin-shelled pods filled with small seeds and silky or cottonlike fiber. The durian, Durio zibethinus L., is one member that differs radically in having large seeds surrounded by fleshy arils. Apart from variants of the word "durian" in native dialects, there are few other vernacular names, though the notorious odor has given rise to the unflattering terms, "civet cat tree", and "civet fruit" in India and "stinkvrucht " in Dutch. Nevertheless the durian is the most important native fruit of southeastern Asia and neighboring islands

The durian tree, reaching 90 to 130 ft (27-40 m) in height in tropical forests, is usually erect with short, straight, rough, peeling trunk to 4 ft (1.2 m) in diameter, and irregular dense or open crown of rough branches, and thin branchlets coated with coppery or gray scales when young. The evergreen, alternate leaves are oblong-lance-olate, or elliptic-obovate, rounded at the base, abruptly pointed at the apex; leathery, dark-green and glossy above, silvery or pale-yellow, and densely covered with gray or reddish-brown, hairy scales on the underside; 2 1/2 to 10 in (6.25-25 cm) long, 1 to 3 1/2 in (2.5-9 cm) wide. Malodorous, whitish to golden-brown, 3-petalled flowers, 2 to 3 in (5-7.5 cm) wide, with 5-lobed, bell-shaped calyx, are borne in pendant clusters of 3 to 30 directly from the old, thick branches or trunk.

The fruits are ovoid or ovoid-oblong to nearly round, 6 to 12 in (15-30 cm) long, 5 to 6 in (12.5-15 cm) wide, and up to 18 lbs (8 kg) in weight. The yellow or yellowish-green rind is thick, tough, semi-woody, and densely set with stout, sharply pointed spines, 3- to 7-sided at the base. Handling without gloves can be painful. Inside there are 5 compartments containing the creamy-white, yellowish, pinkish or orange-colored flesh and 1 to 7 chestnut-like seeds, 3/4 to 2 1/4 in (2-6 cm) long with glossy, red-brown seedcoat. In the best fruits, most seeds are abortive.

There are some odorless cultivars but the flesh of the common durian has a powerful odor which reminded the plant explorer, Otis W. Barrett, of combined cheese, decayed onion and turpentine, or "garlic, Limburger cheese and some spicy sort of resin" but he said that after eating a bit of the pulp "the odor is scarcely noticed." The nature of the flesh is more complex-in the words of Alfred Russel Wallace (much-quoted), it is "a rich custard highly flavored with almonds . . . but there are occasional wafts of flavour that call to mind cream cheese, onion-sauce, sherry wine and other incongruous dishes. Then there is a rich glutinous smoothness in the pulp which nothing else possesses, but which adds to its delicacy. It is neither acid, nor sweet, nor juicy; yet it wants none of these qualities, for it is in itself perfect. It produces no nausea or other bad effect, and the more you eat of it the less you feel inclined to stop." (The Treasury of Botany, Vol. 1, p. 435). Barrett described the flavor as "triplex in effect, first a strong aromatic taste, followed by a delicious sweet flavor, then a strange resinous or balsam-like taste of exquisite but persistent savor."

An American chemist working at the U.S. Rubber Plantations in Sumatra in modem times, was at first reluctant to try eating durian, was finally persuaded and became enthusiastic, declaring it to be "absolutely delicious", something like "a concoction of ice cream, onions, spices, and bananas, all mixed together."

Some fruits split into 5 segments, others do not split, but all fall to the ground when mature.

Initial yield may be 10 - 40 fruits for the first year of fruiting to about 100 fruits for the sixth year. Yield of up to 200 fruits is common after the 10th year of fruiting.

ORIGIN

The durian is believed to be native to Borneo and Sumatra. It is found wild or semi-wild in South Tenasserim, Lower Burma, and around villages in peninsular Malaya, and is commonly cultivated along roads or in orchards from southeastern India and Ceylon to New Guinea. Four hundred years ago, there was a lively trade in durians between Lower Burma to Upper Burma where they were prized in the Royal Palace. Thailand and South Vietnam are important producers of durians. The Association of Durian Growers and Sellers was formed in 1959 to standardize quality and marketing practices. The durian is grown to a limited extent in the southern Philippines, particularly in the Provinces of Mindanao and Sulu. The tree grows splendidly but generally produces few fruits in the Visayas Islands and on the island of Luzon. There are many bearing trees in Zanzibar, a few in Pemba and Hawaii. The durian is not included in the latest Flora of Guam (1970) which covers both indigenous and exotic species. It has been introduced into New Guinea, Tahiti, and Ponape.

The durian is rare in the New World. Seeds from Java were planted at the Federal Experiment Station in Mayaguez, Puerto Rico in 1920. The single resulting tree bloomed heavily in February and March in 1944 but only one fruit matured in July and it had but 3 normal carpels. Nevertheless, there were 6 fully developed seeds which germinated and were planted. The tree has fruited in Dominica and Jamaica. There have been specimens in the Royal Botanic Gardens, Port-au-Spain, Trinidad, for many years though they are not very much at home there. Young trees and seeds were introduced into Honduras from Java in 1926 and 1927, and the trees have grown well at the Lancetilla Experimental Garden at Tela, but they bear poorly to moderately. Seedlings have lived only briefly in southern Florida.

FOLIAGE

The durian tree’s simple, drooping, beautiful leaves are about 3 to 8 inches [8 to 20 cm] long and 1 to 3 inches [2.5-7.5 cm] wide. They are shiny smooth, light or dark green above; the underside is somewhat scaly, sometimes brown but more often a with a golden sheen. The leaves are folded at their mid-rib when they first appear, then stretch out as they mature. The particular shades of green that durian leaves have, combined with the golden sheen of their undersides, give the trees a very attractive and almost glowing appearance.

FLOWERS

Durian flowers, which are strongly fragrant, are 2 to 3 inches [50-70 mm] long and grow in stalked clusters of 1 to 45 individual flowers per cluster. These flower clusters hang from the main and smaller branches, or directly from the trunk of the tree. A period of 3 to 4 weeks dry weather is needed to stimulate flowering. It takes about one month for a durian flower to develop from first appearance as a tiny bud to an open blossom. As it matures, the outer fleshy part of the flower (the epicalyx) splits to reveal 5 united sepals and 5 petals, which match the color of the edible pulp that will develop inside the fruit; trees with yellowish flowers produce yellow-fleshed durians (the most common), while those with white or reddish petals will have white or reddish fleshed fruit. Durian flowers are hermaphrodites, each having a stamen and pistil in the same flower.

However, self-pollination rarely happens, for when the flowers are open, normally from 3 p.m. to about midnight, the pistil and the stamen do not appear at the same time. The female stigma from the pistil usually comes out first, long before the anthers of the stamen appear and shed their pollen; by the time the pollen is active, the stigma is no longer receptive. By midnight most pollen has been shed and all flower parts except the pistil fall to the ground.

Even if the female and male flower parts of durian flowers were active at the same time, most durian trees have a high degree of self-incompatibility. In other words, the flowers must be cross-pollinated from other trees in order to set fruit. (Some clones may have been produced that are self-compatible, however.)

Although durian flowers are much visited by many insects including bees, moths, gnats, and ants, botanists say that durian flower structures are characteristic of the type designed for pollination by bats during the evening. It is thought that the most important natural pollinators of durian trees in southeast Asia are moths and small bats (mainly Eoncyteris spelea), which transfer pollen when they visit the flowers for nectar. Honeybees come to the flowers, but generally too early (before pollen is available) to serve as pollinators.

FRUITS

Botanically speaking, the durian fruit is actually a capsule, and the edible sections are technically called arils. Arillate fruits are rare, perhaps 1% of all tropical fruits. Most fleshy fruits are categorized as drupes (like a plum, with a single hard pit) or pomes (like an apple, with accessory flesh around a seedy core) or berries (including common sweet berries as well as grapes and tomatoes). In an arillate fruit, the aril is a fleshy outgrowth of the seed’s own outer covering. The flesh or aril starts to form 4 weeks after flower pollination; it starts as a white sheet then expands to cover the whole seed. The aril or pulp varies extensively between cultivars and different seedlings in color, aroma, flavor, texture, thickness, and color (usually cream yellow to deep orange, but also rarely in some varieties white and even bright red).

Fruit quality increases with the age of the tree. Bearing durian trees are considered young from age 6 to 15, middle-aged from 15-25, and older after age 25. Durians from trees aged 30, 40, 50, 60 years and more are particularly sought after and savored for their immediately evident enhanced qualities of flavor, aroma, and texture, and can be identified visually by having very wrinkled skin on the fruit sections.

Info Source : International Tropical Fruits Network