Tsuga canadensis (eastern hemlock) description

Conservation status

Tsuga canadensis

(Linnaeus) Carrière 1855

Frequent names

Jap hemlock, Canada hemlock, pruche du Canada (Taylor 1993), hemlock spruce.

Taxonomic notes

Syn: Pinus canadensis Linnaeus 1763 (Taylor 1993).


Timber to 30 m; trunk to 150 cm dbh; crown broadly conic. Bark brownish, scaly and fissured. Twigs yellow-brown, densely pubescent. Buds ovoid, 1.5-2.5 mm. Leaves (5)15-20(25) mm, principally showing 2-ranked, flattened; abaxial floor glaucous, with 2 broad, conspicuous stomatal bands, adaxial floor shiny inexperienced (yellow-green); margins minutely dentate, particularly towards apex. Seed cones ovoid, 1.5-2.5 × 1-1.5 cm; scales ovate to cuneate, 8-12 × 7-10 mm, apex ± spherical, typically projected outward. 2n=24 (Taylor 1993).

Distribution and Ecology

Canada: All provinces east from Ontario, besides Newfoundland; USA: All states E from Minnesota, Wisconsin, Indiana, Kentucky, Tennessee and Alabama besides Florida; at 600-1800 m elevation. Habitat moist rocky ridges, ravines, and hillsides (Taylor 1993). See additionally Thompson et al. (1999). Hardy to Zone 4 (chilly hardiness restrict between -34.3°C and -28.9°C) (Bannister and Neuner 2001).

The species is presently experiencing catastrophic vary discount because of infestation by the hemlock wooly adelgid, Adelges tsugae (HWA). This insect pest, launched to North America from Asia in 1924, has been accountable for widespread dieback of Tsuga canadensis forests. The adelgid was a comparatively minor pest till the mid-1980s, confined to components of Virginia, Pennsylvania, New Jersey, New York and Connecticut. Just lately it has begun fast vary extension and now happens all through a lot of the vary of Tsuga canadensis from Georgia to Maine alongside and east of the Appalachian cordillera (USFS 2007); see additionally ENTS (2005). Lately, important progress has been made growing biocontrols for HWA. Though this effort has not been transferring shortly sufficient to save lots of most of the oldest and largest hemlocks, it does supply actual hope that the hemlocks could also be saved earlier than they’re extirpated from a lot of their vary. The biocontrol efforts depend on the introduction of predatory beetles which might be extremely tailored to prey solely upon species of adelgid; essentially the most promising candidates thus far are beetles native to the Pacific Northwest, which sadly are killed by the chilly winters skilled within the northern and extra continental parts of the vary of Tsuga canadensis (Onken and Reardon 2011).

Large tree

The large tree story for this species is one in every of demise and decline. Every big tree has successively fallen sufferer to the hemlock wooly adelgid, and every successive residing big is smaller than the one earlier than. Each one of many 15 largest bushes that had been recognized by about 2007 is now standing useless, and in just a few years extra they are going to be mere logs.

The most important hemlock recorded was positioned in late April 2007 after it had died; it was positioned in higher Caldwell Fork, Cataloochee, North Carolina and was 46.94 m tall with an estimated quantity of 48.1 m3 (Will Blozan e mail 2007.05.05). From 2006 to 2009 the biggest residing hemlock was the Laurel Department Leviathan, dbh 175 cm, peak 46.6 m, stem quantity 44.Eight m3. See Blozan (2006a) for these knowledge, together with an important story and photographs about climbing this big tree. On June 2, 2009, Blozan revisited this tree and located that it had succumbed to the adelgid regardless of a concentrated program of efforts to reserve it by use of an acceptable pesticide therapy (Will Blozan e mail 2009.06.14). At present (2015) the biggest hemlock is the Cheoah Hemlock, found by Rusty Rhea, USFS-NC Forest
Well being Specialist, throughout an aerial predator beetle launch (to fight
hemlock woolly adelgid) within the surrounding grove in Could 2004 (Blozan 2006b). Will Blozan and Jess Riddle subsequently measured the tree at 155 cm dbh and 48.46 m tall (American Forests 2015). The tree has obtained appreciable media consideration and has had a number of remedies for hemlock wooly adelgid, which appears to be conserving it alive (Blozan 2010).

The tallest specimen on document was the Usis Hemlock close to Cataloochee, North Carolina, which was 52.Eight m tall, however which succumbed to the hemlock wooly adelgid in the summertime of 2007 (Will Blozan e mail 2007.11.01). Blozan (2007) offers the main points, together with story and photographs about climbing this tree. The tallest recognized residing tree is now the Noland Mountain hemlock, barely greater than 51.Eight m tall (Will Blozan e mail 2007.11.01).


The oldest tree on document was specimen O39021, collected close to Tionesta, Pennsylvania by Ed Prepare dinner in 1978. The oldest ring on this pattern was crossdated to 1425, making it not less than 554 years outdated (NCDC 2006). The identical website had two different bushes with over 500 years of document.

One other lengthy document had a hoop depend of 515 for a not too long ago minimize tree 15 inches diameter in an old-growth stand at Angola-by-the-Lake in Erie County, New York (Vogel 1997). I’d guess from the small dimension of the tree, in a stand dominated by bushes 30 to 40 inches in diameter, that it spent an excellent a part of its life as advance regeneration.

One tree, sampled within the mid-1980s, had 385 rings at some extent roughly 16 m above the bottom; the middle was destroyed by rot beneath that peak. The tree had fallen at the moment and is thus useless. The time it took to develop to a 16 m peak might have been something from just a few many years to a number of centuries, since hemlocks have the aptitude of persisting as understory bushes for a really very long time earlier than a cover disturbance lets them develop into forest dominants. This outdated tree grew within the Alan Seeger State Forest Monument in central Pennsylvania, in a cove forest that one way or the other escaped the loggers (Gove and Fairweather 1988, J.H. Gove e-mail 1999.02.22).

There are unverifiable information of bushes as much as 988 years outdated. Sources are cited and a dialogue is introduced by ENTS (2012). Though this age is way older than any tree for which knowledge might be shown–and folks have actually appeared for such trees–still the ecological mechanism, of lengthy persistence beneath a closed cover, is ecologically believable and has resulted in bushes of comparable age in Tsuga heterophylla and T. mertensiana.


Work has been accomplished as early as 1941 (Meyer 1941). As of February 1999, there are roughly 60 research involving this species. They primarily contain a various suite of ecological issues together with website high quality, stand improvement, insect assault, acid rain, historic land use, and impacts of anthropogenic local weather change. This has additionally been utilized in reconstructing local weather variation, archeological research and quite a few comparatively esoteric matters. By the way, because of its distinctive pollen morphology, that is a particularly necessary species in reconstructing postglacial vegetation change within the japanese U.S. and Canada.


The wooden is used extensively as development lumber, and tannins produced by the bark had been at one time used for tanning leather-based. The wooden, nevertheless, tends to be brittle and inferior to that of the opposite North American hemlocks (which isn’t notably good wooden usually, in comparison with most species of Pinaceae used for timber, having comparatively low energy and low rot resistance). Quite a few decorative cultivars of Tsuga canadensis have been developed, together with compact shrubs, dwarfs, and swish bushes (Taylor 1993).

Jap hemlock (Tsuga canadensis) is the state tree of Pennsylvania (Taylor 1993).


I’ve seen this species in places from the Nice Smokies Nationwide Park (Tennessee) to Killarney Provincial Park (Ontario). A few of the finest examples I’ve seen had been alongside the Blue Ridge Parkway within the Grandfather Mountain space, the place it may be seen with Pinus strobus and Pinus pungens.

A positive stand has been preserved in Hemlock Bluff Nature Protect in Cary, North Carolina. This disjunct southeastern inhabitants is sufficiently remoted that it has not (as of late 2020) skilled hemlock woolly adelgid infestation, and has many massive and outdated bushes.


The epithet refers to Canada, the supply of the earliest specimens introduced again to Europe.


American Forests. 2015. American Forests Large Tree Register 2015. http://www.americanforests.org/bigtree/eastern-hemlock-tsuga-canadensis-3/, accessed 2015.06.30, now defunct.

Blozan, Will. 2006a. Laurel Department Leviathan climb. www.nativetreesociety.org/tsuga/laurel_branch/laurel_branch_leviathan_climb.htm, accessed 2007.03.30.

Blozan, Will. 2006b. The Cheoah Hemlock. www.nativetreesociety.org/tsuga/cheoah/cheoah_hemlock.htm, accessed 2015.10.21.

Blozan, Will. 2007. The Usis Hemlock Climb. www.nativetreesociety.org/fieldtrips/gsmnp/usis/usis_hemlock_climb.htm, accessed 2007.03.30.

Blozan, Will. 2010. Cheoah Hemlock Aerial Remedy for HWA. www.ents-bbs.org/viewtopic.php?f=106&t=1578, accessed 2015.10.21.

ENTS. 2005. HWA. HWA on the Jap Native Tree Society, accessed 2015.12.27.

ENTS. 2012. A 969-year-old Jap hemlock (Tsuga canadensis). http://www.ents-bbs.org/viewtopic.php?f=150&t=4302, accessed 2013.12.22.

Meyer, H.A. 1941. Progress fluctuations of virgin hemlock from northern Pennsylvania. Tree-Ring Bulletin 7(3):20-23.

[NCDC 2006] Knowledge accessed on the Nationwide Climatic Knowledge Middle World Knowledge Middle for Paleoclimatology Tree-Ring Knowledge Search Web page. http://hurricane.ncdc.noaa.gov/pls/paleo/fm_createpages.treering, accessed 2006.09.08, now defunct.

Onken, B. and R. Reardon. 2011. Implementation and standing of organic management of the hemlock woolly adelgid. FHTET-2011-04, Forest Well being Know-how Enterprise Staff, U.S.D.A. Forest Service. Obtainable: www.fs.fed.us/foresthealth/know-how/, accessed 2015.12.27.

[USFS 2007] United States Forest Service. 2007. Hemlock Woolly Adelgid Web site. http://www.na.fs.fed.us/fhp/hwa/, accessed 2007.03.30.

Vogel, Mike. 1997.08.03. Nature’s Cathedrals. Buffalo Information.

See additionally

Burns and Honkala (1990). An ordinary reference on this species, containing a lot element.

Elwes and Henry 1906-1913 on the Biodiversity Heritage Library (Photographs). This sequence of volumes, privately printed, offers among the most partaking descriptions of conifers ever revealed. Though they solely deal with species cultivated within the U.Ok. and Eire, and the taxonomy is a bit dated, nonetheless these accounts are thorough, treating such matters as species description, vary, varieties, exceptionally outdated or tall specimens, exceptional bushes, and cultivation. Regardless of being over a century outdated, they’re typically correct, and are illustrated with some exceptional images and lithographs.

Hough, R. F. and R. D. Forbes. 1943. The Ecology and Silvics of Forest within the Excessive Plateaus of Pennsylvania. Ecological Monographs 13(3): 299-320. Comprises an account of a stump with 618 rings.

Prasad and Iverson (1999).

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

The Tsuga Search Undertaking of the Jap Native Tree Society, accessed 2007.03.30.

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