Larch and tamarack

Tamarack (Larix laricina) is also commonly called eastern larch. Western larch (Larix occidentalis) also called tamarack. Although larch and tamarack are different species, they are in the same genus and can be used interchangeably.

Tamarack grows throughout the northern U.S. and Canada, from Alaska to Minnesota, Wisconsin, into Pennsylvania, West Virginia and up to Maine. Western larch is found primarily in Montana, Idaho, Oregon and Washington, as well as British Columbia.

Tamarack is a smaller tree, seldom exceeding 75 feet in height, while western larch can exceed 180 feet. Tamarack trees may live for 200 years, while western larch can often exceed 400 years of age. The extremely thick bark (up to 6 inches) allows these trees to survive many forest fires without damage. In the fall, the needles turn lemon-yellow and then drop off, leaving this conifer looking quite bare in the wintertime; most conifers are evergreens. Both species like wetter sites.

Tamarack has certain wildlife values. Porcupines feed on the inner bark, snowshoe hares browse on seed-lings, and red squirrels eat the seeds. Birds common in tamarack stands during the summer include the white-throated and song sparrows, veery, common yellowthroat, and Nashville warbler. The American osprey, a sensitive species, often nests in lowland types such as tamarack. The great gray owl utilizes large tamarack stands in northern Minnesota,

Tamarack and larch lumber is used for local construction, in the region where the trees are grown. It was also used for telephone poles. Its moderate natural decay resistance and inability to be treated easily limited this use. The wood is also used for furniture, flooring and millwork. At times western larch is used interchangeably with Douglas-fir. In Alaska, the small stems of tamarack will be used for dog sled runners; in Alberta, Canada, and in Wisconsin tamarack is prized for making goose and duck decoys.


Processing suggestions and characteristics

Density. This is a moderate weight softwood wood. The green specific gravity 6% MC, is 0.55. or half as dense as water. The weight, when dry, is 34 pounds per cubic foot or about 1.9 pounds per board foot at 3/4 inches thickness for 4/4 S4S lumber.

Drying. The wood dries fairly easily, with some warp and checking. As over-drying results in poor machining, care must be taken to avoid drying under 10 percent MC. Most suppliers will sell only KD stock, rather than green. Closely monitoring incoming MC to avoid over-dry or under-dry stock is certainly prudent.

Gluing and machining. This wood glues easily with conventional adhesives. Some resin exudation on old (not freshly machined) surfaces will cause difficultly with gluing and finishing from time to time.

This wood machines fairly well, although at times the grain is stringy. Dulling of tools may be more rapid than normal life with other softwoods. Shake (splits running with the grain and not across) is a problem defect, either arising from a bacterial infection in the tree or pounding of the tools on over-dried, brittle wood. Work with the supplier to eliminate hokey pieces and get the correct MC.

Stability. Shrinkage in drying is fairly low. Western larch shrinkage from green to 6 percent MC is 6.3 percent tangentially (the width in flatsawn lumber) and 3.4 percent radially (the thickness of flatsawn lumber). Tamarack has slightly less shrinkage: 5.9 percent and 3.0 percent. Once dried, the wood will move very little even if there are large RH changes or if the MC is not matched to the environments EMC conditions. A typical final MC range is 9.5 to 11.5 percent, unless used in a humid location. It takes approximately a 4.5 percent MC change to result in 1 percent size change tangentially and 9 percent MC change radially.

Strength. Due to its moderate density, these species are fairly strong and stiff. For dry tamarack, the ultimate strength (MOR) is 11,600 psi, stiffness (MOE) is 1.64 million psi and hardness is 590 pounds. For western larch, the ultimate strength (MOR) is 13,000 psi, stiffness (MOE) is 1.87 million psi and hardness is 830 pounds. Douglas-fir values are similar: 13,100 psi, 1.79 million psi, and 600 pounds; in fact, sometimes western larch is sold with Douglas-fir. Note: Comparative oak values are 14,300 psi, 1.82 million psi, and 1290 pounds.

Splitting when nailing or screwing, especially with over-dried wood, is common, so predrilled holes may be necessary.

Color and grain. The heartwood is reddish-brown in color. Sapwood, which is white in color, is seldom found in lumber, as it is only a narrow band in the tree. Typical growth rates are very slow, 30 rings per inch or even more. As a result, the wood appears coarse grained.

The wood is odorless, but does have a slightly oily feel.

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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.