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Eucalyptus: the mythical, medicinal wood.

Native to Australia and Tasmania, eucalyptus encompasses a massive number of trees which are important for their oil, gum, fuel, medicines and timber. The eucalyptus genus represents more than 300 species (some sources list more than 500 species) ranging in size from tiny shrubs to trees which grow as tall as sequoias.

Since the mid-1800s some species have been successfully transplanted in Europe, Algeria, Tahiti, Natal, India, South America, South Africa and the United States. Within the United States eucalyptus flourishes in California, Hawaii and Florida. Eucalyptus cordata and Eucalyptus pulverdenta are the young eucalyptus twigs many Americans commonly purchase from florists.

Of myth and medicine

In its native land, eucalyptus inspired myths. Because it has so many uses, ranging from medicine to timber -- and practically everything in between -- the Australian aboriginals were said to believe the trees had mystical powers.

Eucalyptus' medicinal powers are also said to be legendary. According to the Encyclopedia of Wood, "The leaf glands of many species, especially Eucalyptus salicifolia and Eucalyptus globulus, contain a volatile aromatic straw-colored oil which can be extracted by steam distillation and should contain at least 70 percent eucalyptus. The chief use is as an expectorant ... and is also used to relieve colds and asthma.

"Botany Bay king, an amorphous resin, is obtained from incision in the same trees; gum is readily derived from Eucalyptus gigantea, while a hard opaque substance known as manna, is procured from other species."

Another facet to eucalyptus is its water conservation. In fact, some species are so adept at conserving water in their root system that they become a source of water for people in the desert.

In California, eucalyptus trees are planted around fruit groves to shield the trees from the wind. Domestically, lumber uses include material for ships, railroad ties, paving blocks, telegraph poles, fences, posts, furniture and veneers.

But while eucalyptus has many positive attributes, it also has some negatives. The Encyclopedia of Wood states, "Though loved in the Antipodes, eucalyptus has come to be abhorred in Madagascar: The climate appears to be especially benign, and it grows voraciously. In contrast to parts of the world where timber conservation is the aim, Madagascar is gradually being taken over by the weed-like tree which cuts the light from indigenous flora and rampantly colonizes whenever it can."

Diverse uses for karri and jarrah

According to the Encyclopedia of Wood, Tasmanian oak is the export name for three eucalyptus trees known locally as ash (jarrah, karri, spotted gum), but having no connection with European oak or ash. Jarrah is the most durable of the species, and being impervious to parasites and not particularly decorative, it has been found ideal for docks, harbors, and bridges." Even in the 19th century, London engineers specified the wood for use as ties in the railway underground.

Jarrah and karri are the most commercially important trees from Australia. Karri is one of the species of eucalyptus trees that grows to an immense height -- nearly 300 feet with diameters of 6 to 10 feet and no branches for the first 80 to 100 feet. It is similar to jarrah, which is cut more often than any other commercial tree in Australia.

Karri is a reddish brown wood with an interlocked grain and is sometimes cut for higher grades. Quartered surfaces yield an attractive striped figure that works well for cabinetry, furniture, veneer and paneling.

Curly jarrah is the term for the jarrah that produces a curly figure, which is especially popular for cutting into decorative veneers. Jarrah has been compared to American mahogany because it has a rich red color that will deepen with age and exposure.

Karri is considered the stronger of the two woods. However, jarrah is better for outdoor uses, especially where the wood is buried or used underwater, such as for dock posts or ships' hulls. Karri is susceptible to the elements and to attack by fungi, marine borers or termites.

But while jarrah can be used in underwater applications, karri is recommended for uses above water, i.e., wharfs and bridges. As a construction wood it is used for joists, rafters and heavy load-bearing beams.

Another important eucalyptus tree indigenous to Australia is the Eucalyptus maculata, also known as spotted gum. It is light in color and has been used as a substitute for satinwood, although it is not considered its equal in all properties. Spotted gum is used for heavy construction, flooring and shipbuilding, including stems, framing, planking and stern posts. Spotted gum is also used for cabinet-making and furniture.

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Family Name

Eucalyptus diversicolor of the Family Myrtaceae

Other Names

Karri. Related species is Eucalyptus marginata, also known as jarrah.

Height/Weight

Karri can grow as tall as 280 feet with an average weight of 55 pounds per cubic foot. Jarrah is much shorter with average heights of 100 to 50 pounds per cubic foot (with a weight range between 43 and 65 pounds per cubic foot).

Properties

Karri must be dried with care or the end result is deep checking and distortion. It is a very heavy wood and earns high marks for strength. Steam-bending capabilities are moderate. It is difficult to work with hand tools due to its wavy, interlocked grain. It can blunt cutting surfaces and requires pre-boring for nailing. Karri glues well. Once filled, it will finish very well. The wood has a moderately coarse but even texture.
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Copyright 1996, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Title Annotation:Wood of the Month
Author:Kaiser, Jo-Ann
Publication:Wood & Wood Products
Date:Oct 1, 1996
Words:900
Previous Article:21st Century designers debut at IWF '96.
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