Eastern hemlock (Tsuga canadensis): what the agencies record

This page reports what US federal publications say about one tree. It does not identify trees from descriptions or photos and does not say what should be done with any tree. The family overview, tree species in the agency records, explains the sources and holds the comparison table.

At a glance

Item	What the source records
Scientific name	Tsuga canadensis (L.) Carriere, pine family
Other names	Canada hemlock and hemlock spruce (Silvics); Canadian hemlock (Wood Handbook)
Native status, USDA PLANTS	Native in Canada and in the lower 48 states
Typical size in stands, Silvics	Ages approaching 400 years, trunk diameters of 89 to 102 cm (35 to 40 in) and heights above 30 m (100 ft)
Lifespan, Silvics	May take 250 to 300 years to reach maturity and may live 800 years or more; the record age reported is 988 years
Green weight of the wood, NRS-38	50 lb per cubic foot, without bark

Native range

The Silvics of North America handbook (Agriculture Handbook 654, volume 1, 1990) gives the northern limit of eastern hemlock as running from outliers in northeastern Minnesota and the western third of Wisconsin east through northern Michigan, south-central Ontario and extreme southern Quebec to New Brunswick and all of Nova Scotia. In the United States it says the species is found throughout New England, New York, Pennsylvania and the middle Atlantic states, from central New Jersey west to the Appalachians and south into northern Georgia and Alabama, with outliers in extreme southern Michigan and western Ohio and scattered islands in southern Indiana. The range overlaps that of Carolina hemlock, a closely related species limited to the slopes of the Appalachians from Virginia and West Virginia into Georgia. The handbook says the species is restricted to cool, humid climates and that commercial volumes have been greatly reduced by harvesting. In Michigan, sawtimber volume fell 69 percent between 1935 and 1955.

Growth, size and age

Silvics calls eastern hemlock a slow-growing, long-lived tree that, unlike many trees, grows well in shade. Early growth is so slow that trees under 2.5 cm (1 in) in diameter may be as old as 100 years and saplings of 5 to 8 cm (2 to 3 in) may be 200 years old. One 26 cm (10.3 in) tree in a dense stand was 359 years old. The handbook says many trees may be suppressed for as long as 200 years yet keep good stem form. The largest recorded diameter is 213 cm (84 in) and the maximum height 49 m (160 ft); another tree measuring 193 cm (76 in) across and 53.3 m (175 ft) tall is called among the largest recorded. It adds that yields of eastern hemlock tend to be higher than in most forest types except white pine and red pine.

Flowers and cones

The handbook describes the species as monoecious, with male and female flowers in separate clusters on the same branch. Male flowers begin to form at about age 15, and flowering runs from late April to early June depending on locality and season. Cones reach full size in late August to early September, open fully in mid-October, and seed dispersal extends into the winter. Silvics says the pollen is extremely sensitive to drying, often the cause of seed failure.

Roots

Silvics says site conditions largely decide rooting: root systems are shallow where the water table is near the surface, and deeper rooting may be seen on better-drained sites. It also says heavy cutting leaves trees more open to windthrow because of the shallow rooting habit.

Wood

The Wood Handbook (FPL-GTR-282, 2021) says the heartwood of eastern hemlock is pale brown with a reddish hue and that the sapwood is not distinctly separated from it. It describes the wood as coarse and uneven in texture, with old trees tending to have considerable shake, and as moderately lightweight, moderately hard, moderately low in strength, moderately stiff and moderately low in shock resistance. It says the species is used principally for lumber and pulpwood, with the lumber going mainly into framing, sheathing, subflooring, roof boards, boxes, pallets and crates. Silvics adds that the bark was once a source of tannin for the leather industry.

Wood Handbook figure	Green	At 12% moisture content
Specific gravity (Table 5-3b)	0.38	0.40
Modulus of rupture, lbf per square inch (Table 5-3b)	6,400	8,900
Side hardness, lbf (Table 5-3b)	400	500
Moisture content of green wood, percent (Table 4-1)	97 heartwood, 119 sapwood	Not applicable

The green weight of the wood is in the NRS-38 table, the same figure used in the log weight calculator.

Pests and diseases the sources name

Silvics (1990) says at least 24 insects attack eastern hemlock but few are economically important. It names these agents by the names it used.

Hemlock borer. Melanophila fulvoguttata, named as the most important insect, which the handbook says attacks weakened trees. It lists woodpecker-like holes in the bark, galleries filled with dark excrement and yellowing shoot tips as the symptoms.
Defoliators and scale. Spruce budworm, hemlock looper, hemlock scale, and gypsy moth, which the handbook says kills understory trees in the eastern states.
Needle and twig diseases. A rust named Melampsora farlowii, which it calls one of the most damaging, three needle rusts, a single-needle browning caused by Fabrella tsugae, and a sooty growth from Dimerosporium tsugae.
Decay. Heartwood attacked by Uromyces borealis, cavity-forming Pholiota adiposa in the Lake States, and rots from Haematostereum sanguinolentum, Phellinus pini and P. robustus. Ganoderma tsugae is called the most common decayer of stumps and old logs.
Roots. Armillaria mellea, Phaeolus schweinitzii, Heterobasidion annosum and others, which the handbook says rarely develop conks or kill trees. Damping-off fungi and root rots are named as the chief threats to seedlings.
Animals and weather. White-tailed deer browse, snowshoe hares, porcupines (bark gnawing causing wounds and top-kill) and sapsuckers (associated with ring shake). Silvics calls drought probably the most serious damaging agent.

The Wood Handbook adds a pest the 1990 handbook does not name: it says the hemlock woolly adelgid, an insect introduced from East Asia, affects hemlock in the southern part of its range, and that the IUCN has classified the species as near threatened. The agencies' wording on that insect is in the guide on hemlock woolly adelgid. Suspected sightings of regulated pests go to the offices on the United States reporting page or the Canada reporting page. Who may apply pesticides is in pesticide licences by country.