The durian is the fruit of several tree species belonging to the genus Durio. There are 30 recognised Durio species, at least nine of which produce edible fruit, with over 100 named varieties in Indonesia, 300 in Thailand and 100 in Malaysia. Durio zibethinus is the only species available in the international market: other species are sold in their local regions.
Regarded by many people in Southeast Asia as the "king of fruits", the durian is distinctive for its large size, strong odour, and thorn-covered rind. The fruit can grow as large as 30 centimetres (12 in) long and 15 centimetres (6 in) in diameter, and it typically weighs one to three kilograms (2 to 7 lb). Its shape ranges from
oblong to round, the colour of its husk green to brown, and its flesh pale yellow to red, depending on the species.
Some people regard the durian as having a pleasantly sweet fragrance, whereas others find the aroma overpowering with an unpleasant odour. The smell evokes reactions from deep appreciation to intense disgust, and has been described variously as rotten onions, turpentine, and raw sewage. The persistence of its odour, which may linger for several days, has led to the fruit's banishment from certain hotels and public transportation in southeast Asia. By contrast, the nineteenth-century British naturalist Alfred Russel Wallace described its flesh as "a rich custard highly flavoured with almonds". The flesh can be consumed at various stages of ripeness, and it is used to flavour a wide variety of savoury and sweet desserts in southeast Asian cuisines. The seeds can also be eaten when cooked.
Durian trees are large, growing to 25–50 metres (82–164 ft) in height depending on the species. The leaves are evergreen, elliptic to oblong and 10–18 centimetres (3.9–7.1 inches) long. The flowers are produced in three to thirty clusters together on large branches and directly on the trunk with each flower having a calyx (sepals) and five (rarely four or six) petals. Durian trees have one or two flowering and fruiting periods per year, although the timing varies depending on the species, cultivars, and localities. A typical durian tree can bear fruit after four or five years. The durian fruit can hang from any branch, and matures roughly three months after pollination. The fruit can grow up to 30 centimetres (12 in) long and 15 centimetres (6 in) in diameter, and typically weighs one to three kilograms (2 to 7 lb). Its shape ranges from oblong to round, the colour of its husk green to brown, and its flesh pale-yellow to red, depending on the species. Among the thirty known species of Durio, nine of them have been identified as producing edible fruits: D. zibethinus, D. dulcis, D. grandiflorus, D. graveolens, D. kutejensis, Durio lowianus, D. macrantha, D. oxleyanus and D. testudinarius. There are many species for which the fruit has never been collected or properly examined, however, so other species with edible fruit may exist. The durian is somewhat similar in appearance to the jackfruit, an unrelated species.
The name durian comes from the Malay word duri (thorn) together with the suffix -an (for building a noun in Malay). D. zibethinus is the only species commercially cultivated on a large scale and available outside of its native region. Since this species is open-pollinated, it shows considerable diversity in fruit colour and odour, size of flesh and seed, and tree phenology. In the species name, zibethinus refers to the Indian civet, Viverra zibetha. There is disagreement over whether this name, bestowed by Linnaeus, refers to civets being so fond of the durian that the fruit was used as bait to entrap them, or to the durian smelling like the civet.
Durian flowers are large and feathery with copious nectar, and give off a heavy, sour, and buttery odour. These features are typical of flowers pollinated by certain species of bats that eat nectar and pollen. According to research conducted in Malaysia in the 1970s, durians were pollinated almost exclusively by cave fruit bats (Eonycteris spelaea); however, a 1996 study indicated two species, D. grandiflorus and D. oblongus, were pollinated by spiderhunters (Nectariniidae) and another species, D. kutejensis, was pollinated by giant honey bees and birds as well as bats.
Some scientists have hypothesised that the development of monothecate anthers and larger flowers (compared to those of the remaining genera in Durioneae) in the clade consisting of Durio, Boschia, and Cullenia was in conjunction with a transition from beetle pollination to vertebrate pollination.