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Home , Acleris gloverana, Tsuga heterophylla

-,.------. A 13.31:H 37/984 Forest An American Service Western United States Department of Agriculture Hemlock FS-240

Western hemlock is an important corn- mercial softwood species in the Western United States and Canada. Thc largest stands are found in the humid coastal regions of Oregon, , , and Alaska. The wood is used for structural , molding, roof decking, veneer, and paper.

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Western Hemlock ( heterophylla (Raf.) Sarg.) James M. Cahill'

Distribution

Western hemlock grows along the Pacific coast from the Kenai Peninsula in Alaska to northwestern (fig. 1). Inland from the coast, it is found on the western slopes and upper eastern slopes of the of Washington and as far south in Oregon as the Siskiyou Mountains.

Farther inland, western hemlock grows on the west side of the Continental Divide from just east of Prince George, British Columbia, south through north- em and northwestern . About 80 percent of its distribution in the is in British Columbia.

The fastest growing stands are found in &O the humid coastal regions of Oregon, Washington, British Columbia, and Alaska, and on the lower slopes of the Cascade Range in Washington and . Oregon. In the Rocky Mountain region, dry summers limit western hemlock to primarily northerly slopes and moist creek bottoms.

I o Western hemlock is usually subordinate in stands that include Sitka spruce () and Douglas- o ioo 200 300

I (Pseudotsuga menziesii), but it I.! I sometimes dominates and is in III,I'i, i-,- found o zoo 400 E pure stands in coastal areas. The pure western hemlock forest is a true climax type and follows the subclimax types of Sitka spruce and Douglas-fir west of the and western white pine // (Pinus monticola) in the northern part / / of its inland range.

Description and Growth

Western hemlock is the largest of the / four American hemlocks and, under the

I . Research Forester, U. S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, Oreg. Figure 1-Natural range of western hemlock. F-532739

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Figure 2-Needles and cones of western F-308997 hemlock.

best growing conditions, can reach The is relatively thin, even on old per cone. The seeds are only more than 3 feet in diameter and 225 , and deeply fissured with broad, 1/16 inch long and average 300,000 feet in height. Forest-grown western flat, russet-brown ridges. The inner per pound. Wind is the main factor in hemlock trees produce long, clear sym- bark is streaked with purple. dissemination; some seeds are metrical boles and shallow, wide- blown more than a mile from their spreading root systems . The crown Western hemlock is a prolific seeder. It source. length of old-growth trees and of produces some seed every year and young, tightly spaced trees is usually heavy seed crops at least every 8 years. With adequate moisture, germination is short. As with all hemlocks, the ter- Cones can be found on trees less than excellent on a diverse range of material minal shoot normally droops, giving it 20 years old, but, in general, cone pro- including moss, humus, decaying litter, look that provides a duction begins between scharacteristic 25 and 30 and mineral soil. In coastal regions, quick method of identification. The years . Cones ripen in late summer and where the forest floor is often densely needles are 1/4 to 3/4 inches long, flat- early fall. At maturity, they are 3/4 to covered with vegetation, hemlock tened, and dark, shiny green (fig. 2). i 1/4 inches long and hold 30 to 40 grows from decaying stumps and logs. An American Wood

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Western hemlock is very tolerant of Related Commercial Species shade and survives under a variety of 2500 seedbed conditions. Natural regenera- Published information on timber tion can be obtained through harvesting volume often includes western hemlock 2250 methods that vary from individual with other species. Estimates of net 2000 selection to clearcutting. sawtimber volume, for 1750 example, . usually include mountain hemlock E 1500 n Oregon and Washington The main causes of hemlock mortality () . Hemlock lumber 2 1250 w are wind, fire, and snow. Losses from is usually marketed in species groups 1000 snowbreak are most severe in the in- such as "Hem-Fir" which includes . land range, whereas significant losses California red fir (Abies magnifica), 750 from windthrow occur in the coastal grand fir (A. grandis), noble fir (A. 500 areas. The shallow root system of procera), Pacific silver fir (A. 25 western hemlock contributes to its amabilis), and white fir (A. C concolor). 1967 1970 1976 susceptibility to fire and wind damage. 1073 1979 Supply Several trunk, butt, and root rots are found on western hemlock: Fomitopsis The sawtimber volume (trees greater Figure 3-Yearly lumber production of western annosus, F. pinicola, Phellinus pini, P. than 9 inches in diameter) of western hemlock, 1967 to 1979. weirii, , Poria hemlock growing in the United States subacida, Echinodontium tinctorium, was estimated to be 256.9 billion board Annillariella mellea, and Polyporus cir- feet in 1 977 . About 45 percent of this cinatus. Echinodontium tinctorium (In- volume was in Alaska, 35 percent in or Oregon lands is prohibited by dian paint fungus) causes extensive Washington, 17 percent in Oregon, and Federal and State laws, with minor decay in standing trees and is one 3 percent in Idaho and Montana. exceptions. reason western hemlock is classified as Mountain hemlock is included in these an inferior species in its inland range. estimates but accounts for only a small The paper industry uses hemlock as a Dwarf mistletoe (Arceuthobium cam- percentage of the total volume. source of pulp. In Washington and pylopodum) is a common parasite and Oregon, hemlock makes up more than is thought to reduce annual growth, Production 50 percent of the volume consumed by lower wood quality, and increase mor- the paper industry. Hemlock logs are tality. The presence of flutes, or deep In the last decade, western hemlock ac- also an important source of veneer vertical grooves with ingrown bark, in counted for more than 20 percent of bolts. In 1976 hemlock accounted for the bole is a problem in southeast the total lumber production in about 5 percent of the total volume Alaska. Extensive fluting decreases Washington and Oregon , and more than peeled for veneer in Oregon and about yields of fiber and limits use of trees 50 percent of the total Alaska produc- i 5 percent of the volume in for sawtimber. that attack tion. Figure 3 shows the yearly produc- Washington. western hemlock include western tion for Washington and Oregon com- hemlock looper (Lambdina fiscellaria bined and for Alaska. Characteristics and Properties lugubrosa) , western black-headed bud- worm ( gloverana) , western Primary products produced in Oregon The heartwood of western hemlock is larch roundheaded borer (Tetropiun and Washington include dimension almost white, with a purplish tinge. velutinum), and the hemlock sawfly lumber, molding stock, and cants The sapwood is sometimes lighter in (Neodiprion tsugae). (squared-off timbers) for export. Alaska color. It varies in thickness from i to 3 production is predominantly cants. inches and is usually difficult to Common Names distinguish from heartwood. Western Western hemlock is the major species hemlock wood is moderately light in Western hemlock has been known by exported from Washington and Oregon weight and moderate in strength, hard- several common names, including west and accounted for more than 50 percent ness, stiffness, and shock resistance. coast hemlock, hemlock spruce, Pacific of all log exports in 1980. The export Shrinkage is moderately large-about hemlock, western hemlock spruce, market is second only to lumber pro- equal to that of Douglas-fir. The western hemlock fir, gray fir, silver duction in log use. Most exported logs average specific gravity is 0.42 based fir, and Alaska pine. Currently, it is are cut from private lands and lands on ovendry weight and green volume; usually referred to as hemlock or managed by the State of Washington. the average weight at 12-percent western hemlock. Exporting logs cut on Federal and State moisture content is 3 1 pounds per cubic An American Wood s

foot. Green western hemlock contains hemlock a preferred species over its where the light color is desirable for

considerably more water than Douglas- major competitors for industrial lumber natural finishes . Western hemlock is fir and requires a longer period of dry- and for finish lumber where even- preferred over Douglas-fir where a ing to reach the same moisture content. wearing and good machining charac- minimum of grain raise, splintering, or teristics are important. annual-ring delamination is important. Ring shake, or the separation of wood Western hemlock ranks only slightly cells in the outer part of the latewood In both nail-holding ability and ten- behind Douglas-fir and western larch in (denser wood, formed late in the grow- dency to split when nailed, western strength, which is one of the reasons it ing season), is more common in hemlock has an intermediate rank. In is widely used in construction. hemlock than in other softwoods. paint-holding ability, it ranks below the Typically, shake is found in the basal cedars and white pines but above The light-colored heartwood makes ex- portion of large hemlock trees and Douglas-fir. The wood is free from cellent newsprint because minimum causes considerable loss of lumber and resin and is classed as nondecay- bleaching is required to establish the veneer. resistant. It contains many small, black desired brightness of paper. Also, the knots that are generally tight. The dark lack of resin in hemlock makes the Western hemlock trees frequently con- streaks sometimes seen in hemlock wood easily pulped by the sulphite tain some wetwood, which means that lumber result from activities of the process, which is sensitive to resin parts of the standing wood have hemlock bark maggot in living trees. content. unusually high moisture levels. Wet- wood, generally, is difficult to dry to a Principal Uses When used in the manufacture of consistent moisture content. Wetwood plywood, western hemlock veneer is is also sometimes associated with ring Western hemlock is used to produce a generally used for inner plys. Öake. wide variety of products. The light col- or of the wood, lack of pitch, and The bark of western hemlock is often Cell wall thickness in the annual ring ability to take a varnish finish well used for decorative horticultural pur- of western hemlock shows no distinct make hemlock the major source of roof poses. As such, it is often preferred change from the wood formed early in decking, particularly in exposed ceil- over the bark of Douglas-fir, which the growing season to wood formed ings. It is also excellent for laminating contains needlelike fibers and causes later. This characteristic makes western stock, moldings, and architectural trim discomfort to handlers.

References trees of the United States. Agric. Packee, E. C. The ecology of western Handb. 271. Washington, DC: U.S. hemlock. In: Proceedings, western Berqvall, J. A. ; Bullington, D. C.; Department of Agriculture; 1965. hemlock management conference; Loren, G. 1976 Washington mill 762 p. 1976 May; Seattle, WA. Seattle, survey-wood consumption and mill Harlow, W. M. ; Harrar, E. S. Tex- WA: University of Washington, Col- characteristics. Olympia, WA: State tbook of dendrology, 5th cd. San lege of Forest Resources; 1976: of Washington, Department of Francisco, CA: McGraw-Hill, Inc.; 10-25. Natural Resources; 1977. 135 1968. p. 512 p. Panshin, A. J. ; de Zeeuw, C. Textbook Cox, D. R. The growing future of Harris, A. S.; Farr, W. A. The forest of wood technology, 3d ed. San western hemlock. In: Proceedings, ecosystem of , forest Francisco, CA: McGraw-Hill; 1970. western hemlock management con- ecology and timber management. 705 p. ference; 1976 May; Seattle, WA. Gen. Tech. Rep. PNW-25. Portland, Ruderman , F . K . Production , prices, Seattle, WA: University of OR: U.S. Department of Agriculture, employment, and trade in northwest Washington, College of Forest Forest Service, Pacific Northwest forest industries, first quarter 1981. Resources; 1976: 293-305. Forest and Range Experiment Sta- Portland, OR: U.S. Department of Fahey, M. D. Some characteristics of tion; 1974. 109 p. Agriculture, Forest Service, Pacific western hemlock wood. In: Pro- Kimmey, J. W. Cull factors for Sitka Northwest Forest and Range Experi- ceedings, western hemlock manage- spruce, western hemlock, and ment Station; 1981. 47 p. ent conference; 1976 May; Seattle, western redcedar in southeast Alaska. Ruth, R. H . ; Harris, A . S. Manage- A. Seattle, WA: University of Stn. Pap. 6. Juneau, AK: U.S. ment of western hemlock-Sitka Washington, College of Forest Department of Agriculture, Forest spruce forests for timber production. Resources; 1976: 285-292. Service, Alaska Forest Research Gen. Tech. Rep. PNW-88. Portland, Fowells, H. A. , comp. Silvics of forest Center; 1956. 31 p. An American Wood

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OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Sta- tion; 1979. 197 p.

Ward, J. C. ; Pong, W. Y. Wetwood in trees: a timber resource problem. Gen. Tech. Rep. PNW-112. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experi- ment Station; 1980. 56 p.

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. February 1984

This publication supersedes an unnumbered American Wood leaflet, Western Hemlock, issued October 1945.

U.S. GOVERNMENT PRINTING OFFICE : 1984 0 - 415-844 (Item 6)