Tsuga heterophylla (western hemlock) description


Detailed drawing by Matt Strieby (2018.03).

Photo 2

A tree ca. 50 m tall and 252 cm dbh, on the banks of the Hoh River in Washington [C.J. Earle, 2019.07.27].

Photo 10

Base of the tree proven above. Though exceptionally massive, it’s in any other case pretty typical of mature bushes [C.J. Earle, 2019.07.27].

Photo 5

Saplings in a western hemlock forest underneath pretty typical climate circumstances within the Olympic Mountains of Washington [C.J. Earle, 2019.04.20].

Photo 11

Very younger seedling establishing on useless wooden, Hoh River valley, Washington [C.J. Earle, 2019.07.26].


Cones [Dr. Linda B. Brubaker].


Bark on a 60 cm diameter tree [C.J. Earle, 2004.07.18].

Photo 4

Foliage on a tree in habitat, Cispus River floodplain, Washington [C.J. Earle, 2013.06.22].


Distribution map (USGS 1999.

Photo 12

The designated massive tree, Wynoochee River valley, Washington [C.J. Earle, 2019.07.26].


This species generally establishes on useless wooden (Douglas-fir on this case) and produces a root system adept at scavenging nitrogen from useless wooden; Staircase, Olympic Nationwide Park [C.J. Earle, 1987.07.23].


This species generally establishes on a “nurse log”; the road of bushes that develop from such a log is named a colonnade. Mount Rainier Nationwide Park, Washington [C.J. Earle, 2018.10.14].


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Conservation status

Tsuga heterophylla

(Rafinesque) Sargent 1898

Widespread names

Western hemlock, Alaska pine (Peattie 1950), pruche de l’ouest (Taylor 1993).

Taxonomic notes

Syn: Abies heterophylla Rafinesque 1832 (Taylor 1993). On the higher elevational limits of its distribution and underneath hectic circumstances, T. heterophylla tends to resemble T. mertensiana, e.g., leaves are much less strictly 2-ranked and stomatal bands on the abaxial leaf surfaces are much less conspicuous than at decrease elevations (Taylor 1993).


Timber to 60 (75) m; trunk to 200 cm dbh; crown narrowly conic. Bark gray-brown, scaly and reasonably fissured. Twigs yellow-brown, finely pubescent. Buds ovoid, gray-brown, 2.5-3.5 mm. Leaves (5)10-20(30) mm, largely showing 2-ranked, flattened; abaxial floor glaucous with 2 broad, conspicuous stomatal bands, adaxial floor shiny inexperienced (yellow-green); margins minutely dentate. Ovulate cones ovoid, (1)1.5-2.5(3) × 1-2.5 cm; scales ovate, 8-15 × 6-10 mm, apex spherical to pointed. 2n=24 (Taylor 1993). Detailed info on pollen, together with photomicrography, might be present in Davis (1999).

Distribution and Ecology

Canada: Alberta and British Columbia; USA: Alaska, Montana, Idaho, Washington, Oregon and California at 0-1830 m elevation in coastal to midmontane forests. It’s a dominant species over a lot of its vary (Taylor 1993). Hardy to Zone 6 (chilly hardiness restrict between -23.2°C and -17.8°C) (Bannister and Neuner 2001). See additionally Thompson et al. (1999).

Tsuga heterophylla is a dominant forest tree inside its vary. In low elevation coastal forests of Washington, Oregon and southern British Columbia, it shares dominance with Picea sitchensis, whereas in barely drier environments from the western Cascade Vary to its japanese vary limits, its main codominant is Pseudotsuga menziesii (Franklin and Dyrness 1988 and pers. obs.). Its position in western coastal forests displays a number of elements. Conifers on the whole do properly within the moist Pacific Northwest as a result of their evergreen behavior permits them to take care of constructive web charges of photosynthesis through the lengthy, moist winters; as a result of a lot of them are very shade-tolerant, capable of survive in a comparatively darkish understory till dying of overstory bushes permits them to proceed their progress; and since the infrequency of stand-destroying disturbance is instantly exploited by these long-lived bushes (Waring and Franklin 1979). Tsuga heterophylla does notably properly on this area as a result of the most typical disturbance within the coastal temperate rainforest is windthrow, which can destroy single bushes or, much less generally, might flatten complete forests throughout massive swathes of the panorama. Tsuga heterophylla seedlings set up preferentially on natural substrates, particularly down wooden. This offers hemlock a major aggressive benefit over Pseudotsuga and Thuja, each of which set up totally on mineral substrates. Picea sitchensis shares the power to readily set up on useless wooden, which is why it’s codominant with hemlock in coastal forests (Harmon and Franklin 1989).

Since 2015, the fungal pathogen Rhizoctonia butinii or “net rot” has more and more been reported in dying of westen hemlock inside its native vary. This seems to be a local pathogen that has develop into extra outstanding as hemlocks are more and more burdened by summer time drought and excessive temperatures, each of that are related to anthropogenic local weather change within the Pacific Northwest. The direct results of drought stress have concurrently develop into a widespread explanation for hemlock dying (Ramsey 2018, Haglund 2019). It appears doubtless that at the moment forecast local weather change will result in a progressive discount within the vary of western hemlock, with results most pronounced within the southwestern portion of its vary, the place forecast moisture deficits could be best (Reilly et al. 2018).

Large tree

Top 55 m, dbh 259 cm, crown unfold 20 m; at Quisitis Level, Pacific Rim Nationwide Park, BC (Stoltmann 1987). Additionally, peak 53 m, dbh 276 cm, crown unfold 20 m, in Olympic Nationwide Park, WA (American Forests 1996). The latter tree is a effective instance of what I name a pilgrimage tree: it has been on the file books for a very long time (since 1947), is situated in a gorgeous place (commonplace for large bushes), shouldn’t be notably troublesome to seek out as a result of quantity of admirers who’ve overwhelmed a path to it, however is rising is a spot that requires some actual dedication to get to. On this case the tree is on the east finish of the Enchanted Valley and requires a couple of 15-mile hike in from the trailhead.

That is one other a type of species (the others are Picea sitchensis and Pseudotsuga menziesii) the place the tallest bushes are simply making an attempt to maintain up with even taller redwoods (Sequoia sempervirens) rising close by. The tallest hemlock identified, 83.34 m, was found in mid-November 2014 by Mario Vaden and Chris Atkins throughout explorations in Prairie Creek Redwoods State Park, California (Mario Vaden e-mail 2014.11.23). Earlier than that, the tallest identified was “Tsunami”, found on the day that the 2011 Japanese tsunami made landfall in close by Crescent Metropolis, at 82.83 meters peak; additionally found by Mario Vaden (Taylor 2011). Earlier than that, the tallest identified hemlock was 78.9 m tall, 140 cm dbh, additionally in Prairie Creek (R. Van Pelt e-mail 1998.03.18). I imagine these bushes are all nonetheless alive, suggesting that hidden on the market someplace within the redwoods are even taller hemlocks.


M.L. Parker discovered a specimen from the Caren Vary (BC) with 1238 rings (R. Van Pelt e-mail 1998.03.18). The species is able to establishing within the forest understory and surviving for very lengthy intervals (centuries) earlier than coming into the forest cover. This ecological setting characterizes a lot of the lifespan of the oldest identified people. Additionally, the oldest (and largest) specimens are typically discovered close to the higher elevation limits of the species, inside subalpine forests. This can be an artifact of long-term local weather change—it’s thought that the Pacific Northwest mountains had been barely hotter and drier through the ‘Medieval Optimum’ of ca. 1100-1250 AD, so optimum progress charges had been attainable at increased elevations—or it could replicate decreased susceptibility to illness brought on by low annual temperatures and mixed-species stand composition.


As of 1999, greater than 20 research had have been printed. About half have handled forest ecological issues together with main succession, fireplace historical past and tree inhabitants dynamics, however there have additionally been research of culturally modified bushes, the impact of volcanic eruptions, the impact of smelter emissions, wooden know-how and even forensic makes use of. As a result of the species usually grows in a forest inside atmosphere, ring width variation is usually decided primarily by the tree’s aggressive standing. Thus, it is a superb species for research of forest structural change throughout improvement of late-successional forests. Nevertheless, as a result of the wooden decays quickly after tree dying, most relationship research should rely completely on inference from residing bushes.


The bark has a excessive tannin content material. Native peoples used it as a tanning agent, pigment and cleaning resolution. The Quileute, for instance, used a hemlock bark extract for tanning hides and soaking spruce-root baskets to make them watertight. Some Coast Salish folks used a pink dye constituted of hemlock bark to paint mountain goat wool and basket supplies, and as a facial beauty and hair remover. Numerous tribes would use the bark to dye fish nets brown, making them invisible to fish. Black and yellow-orange dyes had been additionally derived from the bark. The wooden is reasonably heavy and pretty simple to carve. It was carved into implements resembling spoons, combs and wedges. The Haida made massive feast bowls from the wooden of bent hemlock trunks. The branches had been thought-about a wonderful bedding materials, and had been additionally used to gather herring spawn by putting them in estuaries the place the herring would use them as a spawning substrate. The pitch and the outer and inside bark had been broadly used medicinally (Pojar and Mackinnon 1994).

Tsuga heterophylla is probably the most economically essential timber hemlock. The wooden is superior to that of different hemlocks for constructing functions and is most frequently used for studs and plywood (offered underneath the “hemfir” designation) and laminated beams; it additionally makes wonderful pulp for paper manufacturing. Resulting from uniform grain and constant density, it mills, planes and shapes properly. Decay resistance is low (MacSween n.d.). Giant parts of the Washington and Oregon Coast Ranges, and the Olympic Peninsula of Washington, are managed primarily for Tsuga heterophylla manufacturing. It has additionally been planted for forestry in NW Europe, primarily Britain and Eire, a use that peaked within the mid-20th century and is now in disfavor. It’s regionally naturalised in Britain, with dense regeneration in a number of forests (Harmer et al. 2011). It is usually used as a decorative (USDA hardiness zones 5, inland populations, to 7, coastal populations).


The species might be readily present in its vary from BC to CA. Excellent examples might be discovered all through the lowlands of Olympic Nationwide Park in WA and at Pacific Rim Nationwide Park on Vancouver Island, BC.


Western hemlock is the state tree of Washington (Taylor 1993).


American Forests 1996. The 1996-1997 Nationwide Register of Large Timber. Washington, DC: American Forests.

Davis, Owen Okay. 1999. Pollen Grain Morphology Hemlock., accessed 2000.02.06, now defunct.

Haglund, Noah. 2019. Blight ravages the western hemlock, Washington’s state tree., accessed 2020.10.31.

Harmer, Ralph, Kate Beauchamp, and Geoff Morgan. 2011. Pure regeneration in western hemlock plantations on historical woodland websites. U.Okay. Forestry Fee Analysis Observe FCRN011.

Harmon, M. E. and Jerry F. Franklin. 1989. Tree seedlings on logs in Picea-Tsuga forests of Oregon and Washington. Ecology 70(1):48-59.

MacSween, Peter. [no date]. Woods to know: Hemlock (western)., accessed 2020.10.31.

Ramsey, Amy C. 2018. Forest Well being Replace: Rising Points with Western Hemlock and Douglas-fir., accessed 2020.10.31.

Reilly, Matthew J., Thomas A. Spies, Jeremy Littell, Ramona Butz, and John Kim. 2018. Local weather, Disturbance, and Vulnerability to Vegetation Change within the Northwest Forest Plan Space. V.1, Pp.29-93 in T. A. Spies, P. A. Stine, R. Gravenmier, J. W. Lengthy, and M. J. Reilly, tech. coords., Synthesis of science to tell land administration throughout the Northwest Forest Plan space. Gen. Tech. Rep. PNW-GTR-966. Portland, OR: USFS Pacific Northwest Analysis Station.

Sargent, C. S. 1898. The silva of North America, V. 12. Boston: Houghton Mifflin (p. 73).

Taylor, Michael. 2011. Winter 2011 Newest Information. www.landmarktrees.web, accessed 2011.03.18.

This web page edited with the assistance of M. P. Frankis, 1999.02.

See additionally

British Columbia Ministry of Forests. 1996. Tree E-book: Studying to Acknowledge Timber of British Columbia., accessed 2000.02.06, now defunct.

Burns and Honkala (1990).

Elwes and Henry 1906-1913 on the Biodiversity Heritage Library (as T. albertiana) (Picture). This sequence of volumes, privately printed, supplies a number of the most partaking descriptions of conifers ever printed. Though they solely deal with species cultivated within the U.Okay. and Eire, and the taxonomy is a bit dated, nonetheless these accounts are thorough, treating such subjects as species description, vary, varieties, exceptionally outdated or tall specimens, exceptional bushes, and cultivation. Regardless of being over a century outdated, they’re usually correct, and are illustrated with some exceptional images and lithographs.

MacKinnon et al. (1992).

Sargent (1898) supplies an exceptionally detailed description of this species, with a wonderful illustration.

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