Tsuga mertensiana

Mountain hemlock is valued for its ability to protect watershed.
Photo Credit: © Susan McDougall, USDA-NRCS PLANTS Database.
Tsuga mertensiana
Common Name: mountain hemlock
Other Common Names: alpine hemlock, black hemlock, hemlock spruce
Plant Functional Group: Evergreen conifer
Class > Order > Family: Pinopsida > Pinales > Pinaceae
What does the species look like?

Mountain hemlock is an evergreen, coniferous tree growing 60 to 100 feet tall, or more. Male and female cones are present on the same tree. Cone production begins when the tree matures at about 20 years of age. The small, yellow male cones bear pollen; the female cones start as purple to green and mature to grayish-brown, and are wind-pollinated.

Mountain hemlock prefers cool to cold maritime climates with mild to cold winters and a short, warm to cool growing season. It is found in areas that have a deep, insulating snowpack that accumulates early in the fall. Its typical habitat is the upper montane and subalpine forests of western North America. It is able to grow on soils derived from a wide variety of parent materials, and grows best on loose, coarse-textured, well-drained soils with adequate moisture.
Where is the species found?
States & Provinces
AK, BC, CA, ID, MT, NV, OR, WA
Which phenophases should I observe?
Do you see...?
Needles Breaking needle buds
One or more breaking needle buds are visible on the plant. A needle bud is considered "breaking" once a green needle tip is visible at the end of the bud, but before the first needle from the bud has unfolded and spread away at an angle from the developing stem.
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How many buds are breaking?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • 1,001 to 10,000
  • More than 10,000
Young needles
One or more young, unfolded needles are visible on the plant. A needle is considered "young" and "unfolded" once it has spread away from the developing stem enough that its point of attachment to the stem is visible, but before it has reached full size or turned the darker green color or tougher texture of mature needles on the plant.

How many young needles are present?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • 1,001 to 10,000
  • More than 10,000
Pollen cones Pollen cones
One or more fresh, male pollen cones (strobili) are visible on the plant. Cones have overlapping scales that are initially tightly closed, then spread apart to open the cone and release pollen. Include cones that are unopened or open, but do not include wilted or dried cones that have already released all of their pollen.
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How many fresh pollen cones are present?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • 1,001 to 10,000
  • More than 10,000
Open pollen cones
One or more open, fresh, male pollen cones (strobili) are visible on the plant. Cones are considered "open" when the scales have spread apart to release pollen. Do not include wilted or dried cones that have already released all of their pollen.

What percentage of all fresh pollen cones (unopened plus open) on the plant are open?

  • Less than 5%
  • 5-24%
  • 25-49%
  • 50-74%
  • 75-94%
  • 95% or more
Pollen release
One or more male cones (strobili) on the plant release visible pollen grains when gently shaken or blown into your palm or onto a dark surface.
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How much pollen is released?

  • Little: Only a few grains are released.
  • Some: Many grains are released.
  • Lots: A layer of pollen covers your palm, or a cloud of pollen can be seen in the air when the wind blows

Seed cones Unripe seed cones
One or more unripe, female seed cones are visible on the plant. For Tsuga mertensiana, an unripe seed cone is green, purple or purple-brown with scales closed together.
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How many seed cones are unripe?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • 1,001 to 10,000
  • More than 10,000
Ripe seed cones
One or more ripe, female seed cones are visible on the plant. For Tsuga mertensiana, a seed cone is considered ripe when it has turned brown or dark gray-brown and the scales have begun to spread apart to expose the seeds inside. Do not include empty cones that have already dropped all of their seeds.
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How many seed cones are ripe?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • 1,001 to 10,000
  • More than 10,000
Recent cone or seed drop
One or more seed cones or seeds have dropped or been removed from the plant since your last visit. Do not include empty seed cones that had long ago dropped all of their seeds but remained on the plant.
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How many seed cones have dropped seeds or have completely dropped or been removed from the plant since your last visit?

  • Less than 3
  • 3 to 10
  • 11 to 100
  • 101 to 1,000
  • 1,001 to 10,000
  • More than 10,000
What do these phenophases look like?

There is currently no photoguide available for this species. If you'd like help us create one, use the guidance document and species template provided here. Then send it via email to education@usanpn.org when it is complete.

USDA PLANTS profile for mountain hemlock (USDA Symbol: TSME )