Over The Horizon

On the Scent of Aromatic Wood

For hundreds of years, the resin-infiltrated wood of Aquilaria malaccensis, the karas tree of the Malay Peninsula, has been prized for the incense-like aroma produced when it is burnt. The wood, known as gaharu, has been an important part of many religious ceremonies, and even though the tree is now increasingly difficult to find, its use continues.

A joint project between Industrial Research Limited, HortResearch and the Forest Research Institute of Malaysia (FRIM) is to investigate the mechanism of Gaharu wood formation and to ways of producing it on a sustainable basis through the establishment of plantations. Aquilaria malaccensis in its natural state does not produce the scented wood; it is not until after the tree has been damaged, allowing the entry of micro-organisms, that a resin which produces a pleasant smell when burnt forms, probably as a defensive reaction. The defence reaction does not affect the whole tree, just the area around the wound.

Adrian Spiers, a plant pathologist with HortResearch, and Sarah Reader, a microbiologist with IRL, have been studying just how the scented wood is formed. Within two years they hope to have identified what is responsible for creating the aroma, and to have injected it back into some trees.

"The HortResearch Engineering Group in Hamilton have developed a patented tree injection system which will be used for these injections. Ultimately it is intended to grow these trees in plantations in Malaysia, which will be injected at age four or five, and harvested a year later," says Spiers.

According to Spiers, the scented wood is highly prized and can fetch more than $3,000 a kilogram. The Aquilaria grow in the forest, where the native forest people of Malaysia carve gouges in the trees with machetes, and return a year later to cut out the wood from around the wound. The tree has no commercial value as a timber species, the wood being stringy and light, and degrading quite readily.

"The tree is becoming endangered because many are cut down in the search for the scented wood," says Spiers. "The supply has always been erratic and short, and if an industry can be established it will be good for Malaysia. None of their industries are based on indigenous species. Rubber is from South America, and the oil palm is also from elsewhere, so this is important for Malaysia,"