Tsuga mertensiana

 

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Family: Pinaceae

 

 

 

 

 

 

 

 

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Mountain Hemlock

 

 

 

The genus Tsuga contains about 14 species native to North America [4] and southern and eastern Asia [10]. The word tsuga is the Japanese name for the native hemlocks of Japan. The word mertensiana is named for Karl Heinrich Mertens (1796-1830), German naturalist and physician, who discovered it at Sitka, Alaska.

Other Common Names: Alpine hemlock, alpine spruce, berg-hemlock, black hemlock, mountain hemlock, Olympic fir, Pacific Coast hemlock, Patton's hemlock, Patton's spruce, Prince Albert's fir, tsuga de California, tsuga de Californie, tsuga de l'ouest, tsuga de Patton, tsuga di California, vastamerikansk berg-hemlock, weeping spruce, westamerikanische hemlocktanne, western hemlock, western hemlock spruce, Williamson's spruce.

Distribution: Mountain hemlock is native to the Pacific Coast region from southern Alaska (Kenai Peninsula) southeast through southeastern Alaska and western British Columbia and south in the mountains from western Washington to western Oregon, and the Sierra Nevada to central California. Also in the Rocky Mountain region from southwestern British Columbia south to northeast Oregon, northern Idaho and northwest Montana.

The Tree: Mountain hemlock trees reach heights of 50 to 150 feet, with diameters of 1 to 5 feet. A record is reported at 113 feet tall, with a diameter of 88 inches.

General Wood Characteristics: The heartwood is near white, sometimes with a purple tinge, while the sapwood is somewhat lighter. It is moderately light in weight and moderate in strength, hardness, stiffness and shock resistance. Trees may contain wetwood and/or have ring shake. The wood is intermediate in nail holding ability and has a tendency to split when nailed. It is satisfactory with respect to being glued and in taking stains, polish, varnish and paint.

 

 

Mechanical Properties (2-inch standard)

 

 

 

 

Compression

 

 

 

 

Specific

gravity

MOE

x106 lbf/in2

MOR

lbf/in2

Parallel

lbf/in2

Perpendicular

lbf/in2

WMLa

in-lbf/in3

Hardness

lbf

Shear

lbf/in2

Green

0.42

1.04

6300

2880

370

11.0

470

930

Dry

0.51

1.33

11500

6440

860

10.4

680

1540

aWML = Work to maximum load.

Reference (56).

 

Drying and Shrinkage

Type of shrinkage

Percentage of shrinkage
(green to final moisture content)

0% MC

6% MC

20% MC

Tangential

7.1

NA

NA

Radial

4.4

NA

NA

Volumetric

11.1

NA

NA

References: (56).

Kiln Drying Schedulesa

 

Conventional temperature/moisture content-controlled schedulesa


Condition

4/4, 5/4
stock

6/4 stock

8/4
stock

10/4
stock

12/4
stock

British schedule
4/4 stock

Standard

T12-C5

T11-C5

T11-C4

T8-A4

T8-A3

K

 

 

 

 

 

 

 

aReference (28, 185).

 

Conventional temperature/time-controlled schedulesa

 

Lower grades

Upper grades


Condition

4/4, 5/4 stock

6/4 stock

8/4 stock

4/4, 5/4 stock

6/4 stock

8/4 stock

12/4, 16/4 stock

Standard

291

291

291

NA

NA

NA

NA

aRefer ences (28, 185).

 

High temperaturea


Condition

4/4, 5/4 stock

6/4 stock

8/4 stock


Other products

Standard

400

400

400

NA

aReferences (28, 185).

Working Properties: The wood is intermediate in nail holding ability and has a tendency to split when nailed. It is satisfactory with respect to being glued and in taking stains, polish, varnish and paint.

Durability: Hemlocks are rated as being slightly or nonresistant to heartwood decay.

Preservation: Western hemlock is resistant to preservative treatment (5).

Uses: Roof decking, laminating stock, moldings, architectural trim, general construction, newsprint and plywood.

Toxicity: May cause dermatitis (4,8&13).

 

Additional Reading and References Cited (in parentheses)

1. Boone, R. S.; Kozlik, C. J.; Bois, P. J., and Wengert, E. M. Dry kiln schedules for commercial woods - temperate and tropical. Madison, WI: USDA Forest Service, FPL-GTR-57; 1988.

2. Dallimore, W.; Jackson, A. B., and Harrison, S. G. A handbook of Coniferae and Ginkgoaceae. London, UK: Edward Arnold Ltd.; 1966.

3. Elias, T. S. The complete trees of North America, field guide and natural history. New York, NY: van Nostrand Reinhold Co.; 1980.

4. Hausen, B. M. Woods injurious to human health. A manual. New York, NY: Walter de Gruyter; 1981.

5. Henderson, F. Y. A handbook of softwoods. London: HMSO; 1977.

6. Little, jr. E. L. Checklist of United States trees (native and naturalized). Washington, DC: USGPO, USDA Forest Service, Ag. Handbook No. 541; 1979.

7. Means, J. E. Tsuga mertensiana (Bong.) Carr. Mountain Hemlock. in: Burns, R. M. and Honkala, B. H., tech. coords. Silvics of North America. Volume 1, Conifers. Washington, DC: USDA Forest Service; 1990; pp. 623-634.

8. Mitchell, J. and Rook, A. Botanical dermatology: plants and plant products injurious to the skin. Vancouver, BC: Greenglass Ltd.; 1979.

9. Simpson, W. T. Dry kiln operator's manual. Madison, WI: USDA Forest Service, FPL Ag. Handbook No. 188; 1991.

10. Summitt, R. and Sliker, A. CRC handbook of materials science. Vol. 4. Boca Raton, FL: CRC Press, Inc.; 1980.

11. Taylor, R. J. The relationship and origin of Tsuga heterophylla and Tsuga mertensiana based on phytochemical and morphological interpretations. Am. J. Bot. 1972; 59(2):149-157.

12. USDA. Wood handbook: wood as an engineering material. Madison, WI: USDA Forest Service, FPL Ag. Handbook No. 72; 1974.

13. Woods, B. and Calnan, C. D. Toxic woods. British Journal of Dermatology. 1976; 95(13):1-97.

14. Youngs, R. L. Strength and related properties of mountain hemlock. Madison, WI, USA.: USDA Forest Service, Forest Products Laboratory, Research Paper FPL3.; 1963.