Hemlocks are handsome evergreen trees of the Pinaceae Family that are essential to forests throughout the temperate Northern Hemisphere.
Hemlocks are all of the Tsuga genus, with ten currently accepted species, four of which are native to temperate North America, and the other six are native to temperate Asia.
They thrive in dense wet forests in rocky soils, which is why they are typically found in the mountains in wet climates throughout their range.
They are widely used for making lumber, furniture, and in the paper industry.
In the forests, they provide critical habitat for countless birds and animals.
They are lovely evergreen ornamental trees that can help prevent flooding and soil erosion with their strong roots.
Let’s learn the identifying characteristics of hemlocks and how to tell them apart from other evergreen coniferous trees. We will also examine the different types of hemlocks in detail.
Exploring Hemlock Varieties – 10 Types and Their Distinctive Features
1. Western Hemlock – Tsuga heterophylla
I have fond memories of Western Hemlock from growing up in coastal British Columbia, Canada, where it dominates the coastal forests.
Its delicate-looking needle-like leaves on its droopy branches give the tree a very graceful appearance.
It is the largest hemlock in the world, growing up to 273 ft tall with a trunk diameter of up to 9 ft wide. In cultivation, they usually grow 100 – 165 ft tall.
It is intolerant of heat and drought and should not be grown in dry climates or above USDA Zone 8.
They are fast-growing for hemlock, growing up to 2 ft per year in the sun.
They are long-lived trees, living hundreds of years or more.
It appears to have more resistance to the Woolly Adelgid than other North American species.
Its population is stable and increasing. However, its limited distribution in Alberta, Canada, has it listed as Critically Imperiled there.
Identifying Features of the Western Hemlock
Western Hemlocks are very tall trees with narrowly conical to somewhat columnar crowns. Branches have strongly descending to pendulous tips, particularly as they mature.
Young trees have a nodding central leader.
The thick trunk has gray-brown to reddish-brown scaly bark that thickens and becomes moderately grooved (fissured) when mature.
Twigs are yellow-brown and finely pubescent.
Leaves are 0.4 – 0.8” (0.2 – 1.2”) long but variable on the twigs, flattened in cross-section and mostly appearing in two more or less flattened rows.
The lower leaf surface is glaucous with two broad stomatal bands; sometimes, they are so broad they appear as one thick band. The upper surface is shiny green or sometimes yellow-green, with minutely dentate margins.
Seed cones are greenish-red and maturing to brown, ovoid, 0.4 – 1” long, and nearly as wide with ovate scales 0.3 – 0.6” long.
Often Confused With: It is mostly confused with the Eastern Hemlock, which has a broader crown, less pendulous branches, and leaves that are slightly shorter with often less dense stomatal bands, appearing less light and feathery compared to the Western Hemlock; it also has seed cones that are narrower. Sometimes it is confused with Douglas Fir (Pseudtotsuga mensiezii), but that one can quickly be differentiated by its needle-like leaves that are arranged spirally around the twigs rather than in flat sprays and its exceptionally thick and deeply grooved bark.
Other Common Names: Western Hemlock-Spruce, West Coast Hemlock, Pacific Hemlock, Alaska Pine
Native Area: The Pacific Northwest of North America from coastal central California, north through coastal British Columbia, Canada, to the Kenai Peninsula in Alaska, USA. It also occurs inland in the Northern Rocky Mountains from Idaho and Montana, USA, north to Prince George, British Columbia, Canada.
USDA Growing Zones: 6 – 8
Average Size at Maturity: 100 – 165 ft (to 273 ft tall), 25 – 40 ft spread
2. Eastern Hemlock – Tsuga canadensis
Eastern Hemlock is a relatively fast-growing tree for hemlock and lives fairly long, though not as long as the Western Hemlock.
It has a Christmas tree-like appearance with lots of bright green needle-like leaves densely packed into a pyramidal crown with small brown cones hanging from the branches.
It is a hardy tree that is able to tolerate light drought better than other hemlocks.
Best grown in partial shade to full shade in medium-moist, well-drained soil of any type. It will tolerate full sun in cooler climates (USDA Zones 3 – 4) but requires shade in hot, humid climates south of USDA Zone 6.
Apply a thick layer of mulch each winter.
This tree is highly susceptible to the Hemlock Woolly Adelgid that has infected hemlock forests throughout eastern North America. It is treatable with pesticides.
It is listed as Near Threatened on the IUCN Red List.
Identifying Features of the Eastern Hemlock
Eastern Hemlock is a tall tree with a dense pyramidal or broadly conical crown with horizontal or ascending branches that are somewhat descending at their tips as they mature.
Young trees have a nodding central leader.
It has a thick trunk up to 5 ft wide with brownish bark that is scaly and grooved.
Twigs are yellow-brown and densely pubescent.
Leaves are 0.6 – 0.8” (0.2 – 1”) long with blunt tips, flattened in cross-section, and short petioles twisted at the base to form two more or less flattened rows.
Lower leaf surfaces are glaucous with two broad, thick, or somewhat diffused stomatal bands; upper surfaces are shiny green to yellow-green with minutely dentate margins.
Seed cones are ovoid or broadly ellipsoid, 0.4 – 1” long, about ⅔ as wide with roughly ovate scales 0.3 – 0.47” with tips that often point outward.
Often Confused With: Eastern Hemlock is often confused with Western Hemlock, which has a narrower crown, more pendulous branch tips, wider seed cones, more variable leaf length, and longer leaves that often have much stronger conspicuous stomatal bands than the sometimes more diffused Eastern Hemlock bands.
Other Common Names: Canadian Hemlock, Canada Hemlock, Eastern Hemlock-Spruce, and pruche du Canada (French).
Native Area: Northeastern North America from northeast Minnesota east through southern Quebec to Nova Scotia, south through the Appalachian Mountains to northern Georgia and Alabama; mostly in the mountains but grows at sea level at the northern end of its range.
USDA Growing Zones: 3 – 7
Average Size at Maturity: 40 – 70 ft (to 98 ft) tall, 25 – 30 ft spread
Some Cultivars Available:
- Weeping Hemlock Tsuga canadensis ‘Pendula’ is a small tree (to 15 ft tall) that typically spreads twice as wide as it does tall with strongly pendulous weeping branches, creating a mounding look that looks great in a shady garden. Grows well in USDA Zones 4 – 8. – Image via Fast-Growing-Trees
- Alpha Upright Canadian Hemlock Tsuga canadensis ‘Alpha Upright’ is an upright dwarf cultivar growing only 6 – 8 ft tall and half as wide with branches and leaves down to ground level, making it a fantastic hedge or screen tree that never needs to be pruned, or a small specimen tree for small gardens. – Image via Nature Hills.
Available at: Fast-Growing-Trees & Nature Hills
3. Mountain Hemlock – Tsuga mertensiana
Mountain Hemlock is the second largest hemlock tree, typically growing 100 – 130 ft tall or up to a maximum of 194 ft tall with a trunk diameter up to 6.5 ft wide. In cultivation, it seldom grows more than 60 ft tall.
It is native to mountainous regions of the Pacific Northwest of North America, where it is a common site in high-elevation mixed coniferous forests.
They thrive in areas with heavy winter snowpacks and are sometimes found growing in or next to bogs.
The inner bark is sometimes used medicinally as a diaphoretic, astringent, and diuretic, added to tea to treat colds, flu, diarrhea, and bladder and kidney issues.
Best grown in average, medium-moist, well-drained soil in full sun to full shade.
It appears to have some resistance to the Woolly Adelgid.
It is sensitive to urban pollution and not recommended for city plantings.
Identifying Features of the Mountain Hemlock
Mountain Hemlocks are tall trees with conical crowns that may become somewhat columnar with age. Young trees have a drooping central leader.
Branches are ascending and horizontal, with descending to pendulous tips, particularly as they mature.
The trunks are thick with thick charcoal gray to reddish-brown or purplish-brown scaly bark that becomes deeply grooved when mature.
Twigs are yellow-brown and hairless to densely pubescent.
Leaves are 0.4 – 1.2” long and typically spread radially in all directions from the twig and often curve toward the tip of the twig.
In cross-section, they are somewhat rounded or 4-angled rather than flattened.
Both leaf surfaces are glaucous with inconspicuous stomatal bands, giving them a bluish-green appearance. The margins are entire.
Seed cones are reddish-brown, oblong-cylindric, 1.2 – 2.4” long and half as wide, with broadly fan-shaped scales 0.3 – 0.6” long and wide.
Often Confused With: Mountain Hemlock is often confused with Western Hemlock, which has flattened sprays of leaves that are flattened in cross-section, have strong stomatal bands on the lower surface only, and margins that are finely toothed rather than entire. Carolina Hemlock also has leaves that are often spirally spreading, but it is a rare eastern species with light brown twigs with dark pubescence and leaves with broad conspicuous stomatal bands only on the lower leaf surface rather than inconspicuous bands on both surfaces.
Other Common Names: Sierra Hemlock, Black Hemlock, Patton Spruce, Hemlock-Spruce
Native Area: Pacific Northwest of North America from the High Sierras of California north through the coast of British Columbia, Canada, to the southeastern Alaska coast. It is also found in the Rocky Mountains of northern Idaho and Montana, USA, and southern British Columbia, Canada.
USDA Growing Zones: 5 – 7
Average Size at Maturity: 65 – 130 ft (to 194 ft) tall, 20 – 30 ft spread
4. Carolina Hemlock – Tsuga caroliniana
Carolina Hemlock is a narrow endemic of the eastern USA, growing on rocky slopes and stream beds in the Appalachian Mountains of Virginia south to Georgia.
It is a tall tree reaching 100 ft in the wild but seldom exceeds 60 ft in cultivation.
Unfortunately, this tree is just as susceptible to the Woolly Adelgid as its cousin, the Eastern Hemlock, and it is also susceptible to the elongate hemlock scale.
It is a rare tree, and its wood is not of commercial value, so it is not replanted after logging. This, along with its susceptibility to the Woolly Adelgid, has resulted in its population being listed as Near Threatened on the IUCN Red List.
Best grown in well-drained soil in partial shade.
Wildlife loves these trees; birds and animals use them for habitat and feed on the seeds. Rabbits, porcupines, and beavers love to eat the bark.
Identifying Features of the Carolina Hemlock
The Carolina Hemlock is a tall tree with a thick trunk up to 6.5 ft wide and a conical crown.
The brown bark is scaly and grooved.
Twigs are light brown and thinly pubescent with short, dark hairs.
Leaves are 0.4 – 0.8” long, somewhat flattened to spirally spreading in all directions.
The lower leaf surface is glaucous with two broad conspicuous stomatal bands. The upper surface is shiny bright green; the margins are entire.
Seed cones are ovoid to oblong, 1 – 1.6” long, and about ⅔ as wide with 0.47 – 0.7” oblong scales with rounded tips.
Often Confused With: Carolina Hemlock is mostly confused with the Eastern Hemlock, which has leaves with minutely dentate margins that are arranged more in flattened sprays; it also has yellow-brown twigs with lighter pubescence, and it has shorter seed cones.
Other Common Names: Southern Hemlock
Native Area: Narrow endemic of rocky stream beds and slopes in the Appalachian Mountains from Virginia to Georgia, USA, usually at 2500 – 4500 ft above sea level.
USDA Growing Zones: 4 – 7
Average Size at Maturity: 45 – 80 ft (to 100 ft) tall, 20 – 25 ft spread
5. Taiwan Hemlock – Tsuga chinensis
The Taiwan Hemlock is a tall evergreen coniferous species that grows up to a height of 150 feet and 5 feet wide.
It has a pyramidal crown with lots of rich glossy olive-green leaves.
It is highly resistant to the Woolly Adelgid, probably the best of all hemlocks, and its use in cultivation has increased recently for this reason.
The wood is widely used for lumber and furniture making, and its aromatic branches, bark, and roots are used to make pleasant-smelling aromatic oils.
Best grown in any well-drained soil of any type; it tolerates highly acidic soils.
It can be grown in partial shade, full shade, or full sun.
The bark is used medicinally in many of the same ways as Mountain Hemlock.
Identifying Features of the Taiwan Hemlock
Taiwan Hemlock is a highly variable species. It is a tall tree with a pyramidal crown and thick trunk up to 5.3 ft wide.
The bark is dark gray and scaly, sometimes exfoliating, and has vertical grooves as it matures.
Twigs are yellow-brown or grayish-yellow and pubescent, maturing to gray or brownish-gray.
The narrow leaves are 0.47 – 1.1” long with obtuse or emarginate tips. They are arranged in flattened sprays or sometimes more radially spreading.
Lower leaf surfaces are grayish-green with stomatal bands. The upper surface is grooved and rich glossy olive green; the margins are entire.
Seed cones are light green, maturing to gray-yellow or pale brown, ovoid-globose to cylindric or obovoid-oblong, 0.6 – 1.6” long, about ⅔ as wide with 0.35 – 0.47” long scales.
Often Confused With: Taiwan Hemlock is sometimes confused with the Himalayan Hemlock, which has lighter-colored bark, twigs that are ridged and grooved, often shorter leaves that sometimes have minutely serrated margins, and shorter seed cones.
Other Common Names: Chinese Hemlock, tieshan (simplified Chinese: 铁杉; traditional Chinese: 鐵杉; pinyin: tiěshān)
Native Area: China, Taiwan, Tibet, and Vietnam.
USDA Growing Zones: 5 – 9
Average Size at Maturity: 130 – 165 ft tall, 25 – 35 ft spread
6. Southern Japanese Hemlock – Tsuga sieboldii
Southern Japanese Hemlock is a tall coniferous tree with a very thick trunk, up to 8 ft wide at 100 ft tall.
It can grow as a single-stemmed tree or occasionally as a multi-trunked tree.
It is native to four islands in Japan and one South Korean island, where they thrive on mountain slopes and ridges from 1300 – 5200 ft in moist, maritime climates.
It typically grows in mixed coniferous forests, providing critical habitat and food for numerous birds and animals.
Best grown in moist, well-drained soils that are somewhat acidic. It can be grown in full sun or partial shade but generally is not grown in full shade like other hemlocks.
It is a popular ornamental tree in Japan, where it is used for screening or as a specimen tree.
It is occasionally used in bonsai.
It is listed as Near Threatened on the IUCN Red List.
Identifying Features of the Southern Japanese Hemlock
Southern Japanese Hemlock is a tall single or multi-trunked tree with a straight or curved trunk up to 8 ft wide.
The crown is broadly conical but becomes irregular and flat-topped with age.
The gray-brown to gray bark is rough and scaly with more or less rectangular plates.
Twigs are hairless and light brown, aging to gray.
Leaves are variable in length from 0.3 – 0.5” long and widen gradually towards their notched tips. Their margins are entire, and they are arranged in two more or less flattened rows.
The upper surface is rich, glossy green, while the lower surface is glaucous with two broad stomatal bands.
Seed cones are 0.8 – 1” long, usually about half as wide producing an oblong to elliptical shape. They are on 0.08 – 0.16” stalks.
Often Confused With: Southern Japanese Hemlock is most often confused with the Northern Japanese Hemlock, which has even shorter leaves grooved on the upper surface and notched tips and may be arranged in flattened rows or spirally spreading; its seed cones are also nearly stalkless. Sometimes it is confused with Carolina Hemlock, but that one has longer leaves that are not grooved on the upper surface and do not have notched tips.
Other Common Names: Siebold Hemlock, Tsuga (栂 – Japanese), Toga matsu
Native Area: Japanese islands of Honshu, Shikoku, Kyushu, and Yakushima, as well as the South Korean island of Ulleungdo.
USDA Growing Zones: 6 – 8
Average Size at Maturity: 40 – 50 ft (to 100 ft) tall, 15 – 25 ft spread
7. Northern Japanese Hemlock – Tsuga diversifolia
The Northern Japanese Hemlock is a medium-sized tree with a pyramidal to somewhat rounded form. It can grow to 90 ft tall in its native habitat but seldom grows over 40 ft in cultivation.
It is a hardy tree that can be grown in partial to full shade, tolerating heavy shade well, although it will grow more slowly there.
It can also be grown in full sun in the cooler climates in its range (USDA Zones 4 – 5) but should not be grown in full sun in warmer climates where the leaves may scorch.
Its compact size makes it a great garden specimen or border tree.
It prefers moist, well-drained soil of any type.
This species shows good resistance to the Woolly Adelgid.
Identifying Features of the Northern Japanese Hemlock
Northern Japanese Hemlock is a medium-sized tree, occasionally reaching heights of 90 ft in its native habitat, but in cultivation, it usually stays under 40 ft and often grows as a smaller, shrubby tree.
It has a pyramidal to conical crown and orange-brown bark with some shallow grooves on mature trees.
Leaves are the smallest among hemlocks at only 0.38” long but are often relatively wide in comparison to their length, making them look like plump green rice grains. They are somewhat flattened into two rows but also may spread radially.
Leaves are glossy green, grooved on the upper surface, and have two white stomatal bands on the lower surface. The tips are notched.
Twigs are reddish-brown, pubescent, and slightly twisted.
Seed cones are ovoid to about 1” long, nearly sessile (stalkless), and dark brown when mature.
Often Confused With: Northern Japanese Hemlock is mostly confused with the Southern Japanese Hemlock, which has slightly longer leaves that are not notched at the tips and do not have grooves on the upper surface, and its seed cones are stalked rather than nearly sessile.
Other Common Names: Kome-tsuga (米栂 – Japanese),
Native Area: Endemic to northern Japan, often growing in mountainous areas near the tree line.
USDA Growing Zones: 4 – 7
Average Size at Maturity: 30 – 40 ft (to 90 ft) tall, 15 – 20 ft spread
8. Himalayan Hemlock – Tsuga dumosa
The Himalayan Hemlock is a tall tree growing to 75 ft tall, with some specimens reaching 130 ft with a 6 ft trunk.
It is widely used in its native range for furniture making. In Europe and North America, it is used mostly as an ornamental tree.
Their branching is more sparse than other hemlocks, even right up into the crown, creating a more open crown, and on mature specimens, it is often covered with moss and other epiphytes.
They are adapted to warmer climates than most hemlocks, growing in USDA Zones 8 – 9, where they perform well in areas with lots of rainfall and high humidity.
Best grown in any average well-drained soil with medium moisture. It tolerates slightly acidic to slightly alkaline conditions.
Best grown in full sun to partial shade. Partial shade is best in areas with hot summers to prevent leaf scorch.
Identifying Features of the Himalayan Hemlock
The Himalayan Hemlock is a moderately tall tree with a pyramidal crown that becomes open, irregular, or sometimes flattened as it ages.
It has a moderately thick trunk with brownish-gray or gray-brown bark that is thick and longitudinally grooved.
Twigs are yellowish or reddish brown, ridged and grooved, turning light brown or dark gray when mature.
Leaves are narrow and needle-like, rarely somewhat lanceolate, 0.4 – 1.4” long. They are grooved on the upper surface and have whitish stomatal bands on the lower surface. Margins are entire or slightly serrated. Tips are obtuse or occasionally emarginate.
Seed cones are light green, maturing to light brown, narrowly ovoid, 0.6 – 1.2” long, and ⅔ as wide with thin, smooth scales 0.4 – 0.6” long.
Often Confused With: The Himalayan Hemlock is sometimes confused with the Carolina Hemlock, which does not have grooves on its leaf surfaces and never has notched tips or serrated margins. It is also confused with the Taiwan Hemlock, which has twigs that are not ridged or grooved, slightly shorter leaves with always entire margins, and longer seed cones.
Other Common Names: Yunnan tieshan (simplified Chinese: 云南铁杉; traditional Chinese: 雲南鐵杉; pinyin: Yúnnán tiěshān)
Native Area: Eastern Himalaya region in Tibet, Vietnam, Bhutan, India, Nepal, Myanmar to Sichuan, China.
USDA Growing Zones: 8 – 9
Average Size at Maturity: 65 – 80 ft (to 130 ft) tall, 20 – 30 ft spread
9. Forrest’s Hemlock – Tsuga forrestii
Forrest’s Hemlock is a tall tree endemic to the mountains of China where it grows in valleys and slopes in mixed forests between 6600 – 9800 ft above sea level.
It is closely related to the Taiwan Hemlock Tsuga chinensis, and some consider it a botanical variety, but plant authorities have designated it as its own species.
It is a beautiful tree with rich green needle-like leaves and attractive purplish-brown seed cones.
It is not currently grown commercially or ornamentally.
It is listed as Vulnerable on the IUCN Red List. It is threatened by ongoing clear-cutting in the region, even though it is not a target species for lumber production there.
Identifying Features of the Forrest’s Hemlock
Forrest’s Hemlock is a medium to tall tree with a relatively narrow trunk up to 3.3 ft wide that often forks in the crown. The crown is conical when young, becoming irregular or flattened when mature.
The bark is orange-brown, rough, and scaly, becoming grooved and brownish-gray on mature trees.
Twigs are red-brown or pinkish-brown, ridged and grooved, pubescent when young, and becoming gray-brown and hairless with age.
Leaves are arranged in two loose rows (not especially flattened), with nearly erect leaves in the center. Leaves are narrow, 0.4 – 1” long, with obtuse to emarginate tips.
The upper surface is glossy green and weakly grooved, while the lower surface has two broad white stomatal bands separated by a prominent midrib.
Seed cones are numerous, sessile or short-stalked, ovoid-oblong, 0.8 – 1.2” long, green and ripening to purplish-brown, then brown. Seed scales are almost round and 0.4” wide.
Often Confused With: Forrest’s Hemlock is mostly confused with the Taiwan Hemlock, which is closely related. Taiwan Hemlock has a thicker trunk with dark gray bark; its leaves are more strongly grooved on their upper surface and are arranged in either flattened rows or radially spreading but do not have the erect central leaves seen in Forrest’s Hemlock, and its seed cones are longer, narrower, and gray-yellow or pale brown.
Other Common Names: Chinese: 丽江铁杉 lijiang tieshan
Native Area: China in the high mountains of NE Guizhou, SW Sichuan, and NW Yunnan.
USDA Growing Zones: 6 – 8
Average Size at Maturity: 50 – 100 ft tall, 20 – 30 ft spread
10. Ulleungdo Hemlock – Tsuga ulleungensis
Ulleungdo Hemlock trees are named after the volcanic island of Ulleungdo in South Korea, where they are endemic to north-facing, well-drained rocky ridges from 1000 – 1650 ft above sea level.
This tree was only discovered to be a new species and described scientifically in 2017 due to ongoing work done in the field to find trees resistant to the Woolly Adelgid.
It had previously been thought to be a variant of the Southern Japanese Hemlock, but upon closer inspection, it was realized that it was a new species, not a variant.
It is a moderately tall tree growing to 72 ft tall with a trunk diameter of up to 2.7 ft wide.
Since it has only recently been discovered, its population status has not yet been assessed. But given its severely limited range, scientists say it would likely be considered critically endangered.
Identifying Features of the Ulleungdo Hemlock
Ulleungdo Hemlock is a tall tree up to 72 ft tall with a trunk up to 2.7 ft wide.
Twigs are thin and hairless.
Leaves are medium-green, narrow, 0.3 – 0.55” long, with relatively long petioles and attenuate bases that gradually narrow down their petioles. Margins are entire and slightly thickened, and the tips are emarginate.
Lower surfaces have two bands of stomata, each with about eight rows of stomata that may or may not be individually visible. There is a single resin canal at the midpoint of the leaf.
Seed cones are purple when young, maturing to brown, rounded to ovoid, 0.75 – 1.2” long, and nearly as wide on short stalks with 0.35 – 0.6” long scales that are nearly as wide.
Often Confused With: Ulleungdo Hemlock is a rare, narrowly isolated tree, but when grown out of its native environment, it could be confused with Northern Japanese Hemlock, which has hairy twigs and pure white stomatal bands, or with Southern Japanese Hemlock, which has thicker leaf resin canals and erose to denticulate rather than more or less smooth cone scale margins.
Other Common Names: N/A
Native Area: Narrow endemic of Ulleungdo Island, South Korea, on north-facing slopes at 1020 – 1640 ft above sea level.
USDA Growing Zones: 6 – 7
Average Size at Maturity: 50 – 72 ft tall, 20 – 25 ft spread
Hemlock Tree Identification (With Photos)
According to the Angiosperm Phylogeny Group, nine currently accepted species of hemlocks are found worldwide.
However, this does not include the brand new species discovered in 2017 called Tsuga ulleungensis, which is endemic to Ulleungdo Island, Korea.
Hemlocks are all part of the Abietoideae or fir subfamily of the pine family, and they share many characteristics with firs. But they are part of a separate tribe within that subfamily, the Pseudolariceae, indicating they also have some important differences.
We will examine those similarities and differences to help us identify the different types of hemlock trees.
Identifying Hemlock Trees by Their Leaf Arrangement
Hemlock trees all have needle-like evergreen leaves. These thin, linear leaves resemble short, plump needles and remain on the tree all year long.
Their leaves are usually spirally arranged on the twigs but twisted to lie in two more or less flat rows, similar to a fir tree.
Sometimes, they are spirally arranged but radially spreading in all directions around the twigs, more like a spruce tree or a Douglas Fir.
Sometimes, there are two somewhat flat rows with shorter needles in the middle of the row that are erect.
And other times, they may be loosely radially spreading but pointing forward, toward the tip of the twig.
Identifying Hemlock Trees by Their Leaf Attachment
Hemlock trees have needle-like leaves with a petiole or leaf stalk, similar to trees with deciduous leaves.
This is an easy way to differentiate hemlock from most other evergreen trees with needle-like leaves.
Fir trees appear superficially similar, especially when the hemlock you are looking at has its leaves arranged in two flat rows. However, fir leaves are attached directly to the branches, making them appear as though they have little suction cups at their ends that hold them on the twigs. That is a way to positively identify a true fir tree.
Spruce trees have radially spreading leaves, similar to some hemlock species. They can be differentiated by their stalk-like pulvinus that attaches their leaves to the twigs. The pulvini sometimes look like petioles, but more often, they are woody and peg-like, which will differentiate them from hemlock. Spruce needles also tend to be very stiff and sharp-pointed at their tip compared to the softer hemlock with more blunt tips.
Pine trees also have needle-like leaves, but they are never attached directly to the twigs and instead are bundled in groups of 2 – 5 (1 – 7) leaves. These bundles are called fascicles, and even if there is only one leaf in the fascicle, it has a conspicuous sheath at its base, identifying it as a pine.
Douglas Fir is the only evergreen tree with needle-like leaves with petioles similar to hemlocks. Their leaves are spirally arranged and radially spreading, like some hemlock species. So, when comparing these two, look for the differently-sized leaves that are typical of hemlock compared to leaves of more uniform length in Douglas Fir. Hemlock leaves also tend to be wider in cross-section (see below).
Identifying Hemlock Trees by Their Leaves in Cross-Section
Most hemlock leaves are flattened in cross-section, similar to true and Douglas Firs. But hemlock leaves tend to be much broader than Douglas Fir and a bit broader than some true firs. These flat leaves cannot be rolled in your fingers.
Some hemlock leaves are nearly round or 4-angled in cross-section, more like most spruce trees. These types of leaves can be rolled in your fingers.
This and other clues can help identify the different types of hemlock trees.
Identifying Hemlock Trees by Their Leaf Tips (Apex)
The shape of their leaf tips can also identify different hemlock tree species.
Hemlock leaf tips are mostly blunt or obtuse. Unlike many other needle-like coniferous leaves, they are never sharp (acute or acuminate).
Often, the leaf tips are emarginate or notched, having a small indent at the tip of the leaf, similar to the Pacific Silver Fir shown in the image below.
The presence of notched tips on hemlock can help to identify certain hemlock species. Asian species tend to have notched tips (with some exceptions), while North American species tend to have more blunt or obtuse tips.
Identifying Hemlock Trees by Their Leaf Margins
Leaf margins can also be helpful in identifying the different types of hemlock trees.
Leaf margins are either entire (smooth, having no teeth), minutely dentate (denticulate – having very small dentate teeth that are sharp or blunt and point outwards away from the leaf), or minutely serrate (serrulate – very small sharp teeth that are typically pointed towards the tip of the leaf).
The margins are typically very hard to see unless you use magnification or have very good eyesight.
But fortunately, there is an easier way to determine to use this feature to help identify hemlocks. When I don’t have my reading glasses or my macro lens, I cannot see the margins well enough to see the teeth, so I simply feel them.
Run your fingers gently down the leaf from the tip to the base. If it feels rough, it has minutely toothed margins. If it is smooth, then it is entire.
Identifying Hemlock Trees by Stomata
Stomata are small pores or openings in the leaf surfaces that allow for gas exchange with the atmosphere, which is critical for photosynthesis.
The stomata of coniferous trees are often coated in wax, making them much more visible. They are also typically arranged in lines that may be diffuse enough to see the individual dots of stomata (magnification may be required), or they may be so dense that they form very conspicuous whitish bands.
Most hemlocks only have stomata on the lower surface. Occasionally there are stomata on the lower and upper surfaces.
The presence of the stomatal bands, how prominent they are, and their location on the leaf are all great clues that we can use to help identify the different types of hemlock trees.
Identifying Hemlock Trees by Their Cones
Hemlock trees, being gymnosperms, do not produce flowers. Instead, they produce cones.
Hemlocks are mostly monoecious, with separate male and female cones on the same tree. Rarely in certain Asian species can they be dioecious with separate male and female cones on separate trees, although the species as a whole is still mostly monoecious.
Pollen cones are quite small and inconspicuous. They are also found in the leaf axils, not at the branch tips, which further hides them. For these reasons, we don’t often use them for identification.
Hemlock seed cones resemble pine cones but in a much smaller size. They are typically around 1” long with about 15 – 30 seed scales.
They are typically ovoid (egg-shaped, widest on the bottom) or occasionally obovoid (like ovoid but widest at the tip), ellipsoid (widest in the middle and narrow at both ends), oblong-cylindric (elongated with more or less parallel sides), nearly rounded (also called globose), or often somewhere in between any of those shapes.
They vary in shape, size, and color, which can help to identify the different species of hemlock trees.
Identifying Hemlock Trees by Their Branches
Hemlock branches are typically horizontal (coming out of the trunk at a 90-degree angle) or ascending (the branches are directed up towards the top of the tree).
However, they often appear descending (directed down to the bottom of the tree) because even though the branches usually come out horizontally or ascending, the tips of the branches descend or even become pendulous (descend so strongly they become vertical). This creates a weeping or drooping appearance.
Identifying Hemlock Trees by Their Twigs
One final feature of hemlock branches to discuss is their twigs.
Twigs are small branches or branchlets located at the ends of the main branches where all the leaves are.
The color of the twigs varies between species, as does whether or not they are pubescent (have hairs) and what the color of those hairs are. These can be useful clues in helping to identify different hemlock species.
Identifying Hemlock Trees by Tree Habit
Tree habit is a tree’s overall form or shape when viewed from a distance.
Hemlock trees typically start out conical (wider on the bottom and narrower at the top, bullet-shaped) or pyramidal (like conical but with a wider and usually flatter bottom, like a pyramid, Christmas tree-like).
As they mature, they may keep those shapes, or more often, they become more columnar (sometimes called cylindrical) as they grow tall but do not spread very wide. Sometimes they may become somewhat rounded in outline. And sometimes, especially as they continue to age even more, they become more irregular with no defined shape, or they may develop a flattened top.
Hemlocks have a unique growth pattern when they are young, where their central leader grows upright but then often droops downward. This is an adaptation to snowy climates since it allows the snow to fall off the top instead of building up and potentially breaking it. As they grow, the top typically straightens out.
Identifying Hemlock Trees by Their Bark
Most bark starts out smooth when it is young. As hemlock trees mature, their bark thickens and takes on one of two characteristic looks.
It could become scaly with rectangular or squarish plates that lift at the edges or rarely exfoliate off in layers.
Or it develops vertical furrows or grooves in the bark separated by ridges. Some develop only shallow grooves, and some develop deep grooves.
Some hemlock species can develop either scales or grooves or sometimes a mix of both, even on the same tree.
Handsome Hemlock Trees
Growing Hemlock Trees in Your Garden
Hemlocks are handsome low-maintenance, healthy trees when grown in the right environment.
Whenever possible, I strongly encourage you to choose species native to your area to enhance biodiversity and wildlife values and reduce the risk of introducing invasive species.
This can be challenging in eastern North America if the Woolly Adelgid is a problem in your area, but those in western North America and temperate Asia have lovely options to choose from.
Fortunately, none of the hemlock species have become invasive outside their native range at this time.
Climate Requirements for Hemlock Trees
Hemlock trees usually have rather narrow climatic ranges, with most thriving only in the USDA 6 – 8 range. A few will grow well down to USDA Zones 4, and one species will grow in USDA Zone 9.
If you are unsure which zone you are in, check out the USDA Planting Zones to determine your zone.
Soil, Water, and Light Requirements for Hemlock Trees
Hemlock trees are not picky about soil type. They will tolerate acidic (often quite acidic) through to somewhat alkaline soils. They all tend to grow naturally in rocky mountainous soils of poor quality.
They have medium moisture requirements, requiring moist, humid climates in order to thrive. None are fully drought-tolerant, and only one species is mildly drought-tolerant. None will thrive in arid or semi-arid environments, even with irrigation.
Though they require medium amounts of water, none will tolerate wet feet since they grow naturally in very rocky, well-drained soils. For this reason, they probably should not be planted in heavy clay soils.
Hemlocks are unique for ornamental trees in their light requirements since most will not tolerate full sun, except in the cooler climates in their range, but all perform exceptionally well in partial shade. Most also perform well, or even thrive, in heavy shade, uncommon for a tree of its size. Their growth will be slower in full shade, but it gives options to those looking for a tree for a very shady spot.
When choosing a tree, compare your chosen tree’s requirements to the site you have for it to ensure it is compatible. A little research ahead of time will save you the hassle of trying to transplant a tree that is not doing well in its location.
You can also check out How to Pick A Tree For Your Yard for more information on choosing the right tree for the right spot in your yard.
Pests and Diseases of Hemlock Trees
Hemlocks, for the most part, are very healthy trees. They can occasionally be prone to needle blight, canker, and rust, as well as bagworms, borers, leaf miners, and spider mites. But none of those tend to be very serious.
The most serious threat is the Hemlock Woolly Adelgid, Adelges tsugae, a tiny (1/32”) sap-sucking insect related to aphids.
It was accidentally introduced to North America in the 1920s in the Pacific Northwest and in the East in the 1950s in Virginia, USA.
It has become a serious threat to eastern North American native hemlocks, which show little to no resistance. It has wiped out much of the old-growth hemlocks in the Great Smoky Mountains National Park and in the Shenandoah National Park.
Perhaps because it has been in the Pacific Northwest longer, or the species there have a natural resistance, it has not become a threat to the western North American species, which are still doing very well.
It is unable to survive cold winters and is so far limited to Massachusetts, USA. However, as the climate continues to warm, it is believed that it will expand northwards into eastern Canada.
The woolly-looking growths on the leaves and twigs will easily identify it, as seen in the photo below.
It is possible to save an infected tree with the use of pesticides, but it is difficult and requires persistence.
Pesticide availability and legality for use vary significantly by region, so if you are facing an infestation, contact your local nurseries to find a suitable product.
Interesting Facts About Hemlock Trees
Western Hemlocks can reach massive heights of 273 ft, heights seen more often in trees like the giant redwoods of California. They are also long-lived, especially at higher elevations, where they can live an estimated 1200 years.
Mountain Hemlocks can reach heights of nearly 200 ft and can live from 500 to an estimated 1400 years.
The oldest known Eastern Hemlock is 559 years old in Pennsylvania, USA.
Poison Hemlock is a completely unrelated plant in the Apiaceae or Carrot Family. Apparently, hemlocks were named after their crushed leaves having a scent similar to the Poison Hemlock plant, not because they contain poisonous compounds. No part of the hemlock tree is poisonous in any way.
Human Uses of Hemlock Trees
Many hemlock species are valuable in the logging industry, where their wood is used for lumber and furniture making or made into pulp for the paper industry.
Western Hemlocks have strong root systems and are sometimes used to help prevent soil erosion and flooding.
The bark of certain species is often used medicinally as a diaphoretic, astringent, and diuretic. The inner bark is harvested and made into tea to treat colds, flu, diarrhea, and bladder and kidney issues.
Taiwan Hemlock’s aromatic branches, bark, and roots are used to make aromatic oils for their pleasant scent.
Hemlocks are grown as low-maintenance ornamental trees where the climate is suitable.
Wildlife Values Hemlock Trees Provide
Hemlock trees provide valuable structural diversity to forests throughout their range.
Old-growth trees, in particular, provide critical habitat for countless birds and animals, including numerous old-growth dependant species.
Mature trees of all sizes also provide critical habitats and roosting sites for birds and arboreal animals outside of old-growth forests.
Numerous birds, native mice, and other rodents routinely feed on the seeds contained within their cones.
Deer and elk routinely feed on the foliage and twigs.
Rabbits, porcupines, squirrels, beavers, and other animals also feed on the bark of the trees.
Hemlocks are beautiful and often overlooked trees that are so critical to the health of our forests. I hope you have enjoyed learning more about these handsome trees. Now you can use your newfound skills to go out and identify the hemlock trees around you!
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