Eucalyptus: the gum from down under.

When you speak of eucalyptus trees you are probably referring to several members of the Myrtaceae family -- most of them natives of Australia. The eucalyptus trees are a varied group, with different characteristics and looks that set them apart from one another. The most widely cut of the timbers is Eucalyptus marginata, commonly known as jarrah. Jarrah's growing range is in the coastal regions of western Australia, south of Perth, and the coastal belt of southwestern Australia.

Jarrah's heartwood is a light red to dark red when freshly cut, but turns a beautiful mahogany-like red upon exposure to air. However, due to its high density and irregular grain, it is considered hard to work with hand and machine tools. Jarrah also has high resistance to cutting tools and a moderate blunting effect. Experts suggest reducing the cutting angle by 15 degrees to prevent tear outs.

Jarrah, and its related species karri and Tasmanian oak, can be finished beautifully. The three prominent eucalyptus species are rotary cut in Australia and used for domestic plywood. Jarrah, with its mahogany-like looks, is good for high-quality veneers and is also used as a turnery wood, because of its attractive grain.

Other uses

Eucalyptus trees are important for timber as well as other products. Trees yield oil and gum that is commercially valuable. The trees have a resin which is sometimes called Botany Bay kino that acts as a natural wood protection against shipworms and other types of borers. Eucalyptus bark from some species produces tannin, an ingredient in medicines. Eucalyptus leaves contain an oil that is used in antiseptic medicines, deodorants and in stimulants. While natives of Australia, the trees have been transplanted successfully in the United States, Chile, New South Wales and Tasmania. Eucalyptus trees have been successfully maintained in the southern United States and in Southern California. They particularly thrive in Florida's warm and humid climate. Those that seem to thrive best in the United States are the blue gum trees or Eucalyptus globulus. Eucalyptus trees grow rapidly and to great heights -- sometimes to gigantic heights and with long lifespans.

Some U.S. eucalyptus are grown for an unusual purpose. In California, orchard owners plant eucalyptus around their cash crops of fruit trees -- such as orange and lemon trees -- as a buffer against the wind.

Tasmanian a pricey choice

Of the many eucalyptus timbers on the market, the most expensive is usually Tasmanian oak, which is rated in the valuable range of the Fine Hardwoods Selectorama.

Although from Tasmania, this wood is not from the Quercus or oak species, but rather from three species of eucalyptus. The species are Eucalyptus delegatensis, which yields alpine ash, white top stringybark, gum-top stringybark and wooly butt; Eucalyptus obliqua or messmate stringybark and brown-top stringybark; and Eucalyptus regnans, also known as mountain ash, stringy gum and swamp gum. It is variously called Australian oak or Tasmanian oak and is often in italics or quotation marks, signifying that it is really neither a true oak nor a true ash.

The heartwood of this tree is light brown with a pinkish cast and a narrow, lighter colored sapwood. Tasmanian oak is the lightwood of the eucalyptus timbers compared with karri and jarrah which are darker and have warm, red tones. Tasmanian oak can have hard gum or "kino veins."

Tasmanian oak varies in weight from 49 pounds per cubic foot for messmate stringybark to 40 pounds per cubic foot for the other species. It is used for furniture and cooperage and is exported as rotary cut decorative veneers. Other uses include interior and exterior joinery, building construction, cladding and weatherboards, sports equipment and flooring.

The karri connection

Karri looks a lot like jarrah. There is a time-honored way of distinguishing the two, however: a simple splinter test. According to the book "The Encyclopedia of Wood," a small burnt splinter of karri forms a thick white ash, while jarrah burns to a black, ashless charcoal.

Karri is an important timber tree that grows in southwestern Australia. It can be gigantic, growing to heights near 300 feet with diameters of up to 10 feet and boles clear of branches up to 80 feet. Its average weight is 55 pounds per cubic foot.

Karri is considered to be stronger than jarrah. Both are good choices for construction work, but karri is not recommended for use under water since it is susceptible to fungal and marine borers as well as termites. Jarrah, because of its unique properties and innate durability, is recommended for marine work and is also used for shingles, and clapboards and for chemical vats. Karri has a red-brown color and an interlocked grain so that the quartered wood has an attractive striped figure. Some karri is cut for architectural quality veneers and used for paneling and high quality cabinetry. Almost all of eucalyptus, karri included, is a good choice for flooring. If karri is treated properly with preservative, the wood can be used for rail poles, piles and sleepers. It is also used for joists, rafters and heavy beams and farm tools. Like jarrah, the wood has an interlocked grain and can be tough to work with hand and power tools. The wood requires preboring when nailing.

Family Names

Eucalyptus marginata, jarrah, of the Family Myrtaceae

Related Species

Eucalyptus diversicolor, karri, Eucalyptus delegatensis, Tasmanian oak

Height/Weight

Weight varies from 43 to 65 pounds per cubic foot; average is 50 pounds per cubic foot. Height range is 100 to 150 feet with trunk diameters of 3 to 5 feet. Specific gravity is 0.80.

Properties

Will check and warp unless mild drying conditions are used. Air-dry first. Kiln schedule T3-C2 recommended for 4/4 stock and T3-C1 for 8/4 stock.