Hevea brasiliensis (rubber tree)
Hevea brasiliensis, better known as the rubber tree, is the primary source of natural rubber.
About this Species
Hevea brasiliensis is native to Brazil (parts of the Amazon Basin and Matto Grosso) and the Guianas, but most of the world's rubber comes from plantations in Indonesia, Thailand and Malaysia. Although rubber is still tapped from wild trees in the Amazon basin, production in South American plantations is hampered by a fungal disease known as South American leaf blight.
The genus Hevea is a member of the family Euphorbiaceae. Only three species of the genus yield usable rubber, Hevea brasiliensis, Hevea guianensis and Hevea benthamiana. Other species have too high a ratio of resin to rubber in their latex. Hevea brasiliensis is the only species planted commercially and is the primary source of natural rubber.
Geography & Distribution
Wild and semi-wild Hevea brasiliensis is found in the northern part of South America, from Brazil to Venezuela, and Colombia to Peru and Bolivia. Rubber is now grown in Malaysia, Indonesia, Thailand, Vietnam, Sri Lanka, China, India and Papua New Guinea in Asia, as well as in Nigeria, Côte d’Ivoire, Cameroon, Liberia and Gabon in Africa.
Hevea brasiliensis seeds (Image: Wolfgang Stuppy)
Hevea brasiliensis is a deciduous tree, typically 30-40 m tall, though usually 15-25 m tall in cultivation, with a leafy crown. The trunk is cylindrical, but frequently swollen towards the base, and the bark is pale to dark brown with a smooth surface and the inner bark pale brown with abundant white or cream coloured latex. The leaves are in spirals and with three leaflets. The flowers are small with no petals, bright or cream-yellow in colour and extremely pungent.They are either male or female but both are found in the same inflorescence. The fruit is an exploding 3-lobed capsule.
In the wild, trees may grow to over 40 m and live for 100 years, but in plantations they rarely exceed 25 m because growth is reduced by tapping for rubber. Plantation trees are usually replanted after 25-35 years when yields fall to an uneconomic level.
Rubber tapping, Cameroon (Image: Andrew McRobb, RBG Kew)
The milky latex of Hevea brasiliensis, produced by a specialised secretory system in the phloem, is the raw material for natural rubber. The latex is a renewable resource that can be sustainably tapped without harming the tree. Rubber is water-resistant, does not conduct electricity, is durable and most importantly, is highly elastic. These useful properties are due to the large and complex molecular structure of rubber.
Rubber has been used for centuries, but its versatility was greatly improved by a process developed in the nineteenth century, vulcanisation, in which the rubber is treated with sulphur and heat. Natural rubber is used in thousands of ways, from bouncing balls, boots, balloons and latex gloves, to engineering and industrial applications. Natural rubber is more suitable than synthetic rubber for the tyres of aircraft and space shuttles.
Felled plantation trees are used for timber – rubberwood – which has important uses in the furniture industry. The seeds contain oil that can be used in making paints and soaps.
Rubber grows best at daytime temperatures of 26°- 28° with a well distributed annual rainfall of 2,000 – 3,000 mm, and up to an altitude of c. 500 m.It will perform well on most soils as long as there is adequate drainage. These conditions are found within 10° N&S of the Equator, although it is cultivated successfully much further north in Mexico, Guatemala and China, and south to near Sao Paulo, Brazil.
This is a tropical tree and requires hot temperatures, high humidity and well-drained, fertile soils. Fruits burst open when they are ripe and the seeds are scattered up to 33 m from the tree. Seed viability drops rapidly as soon as fruits are collected. Best results are obtained with fresh seed grown in partial shade.
This species is difficult to propagate from cuttings; commercial plantations use bud-grafting to propagate plants.
This species at Kew
Two specimens of Hevea brasiliensis can be seen growing in the Palm House at Kew.
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