The Western Hemlock (Alaska Spruce)

The Western Hemlock tree, also known as the Alaska Spruce, is one of the finest trees you will ever see here in the Pacific Northwest. It is so grand, in fact, that it has the distinct honor of being Washington's official state tree. The Western Hemlock is a common conifer tree that grows in the moist, cool forests of the Pacific Northwest. It can also be a good addition to your yard, but only if you have enough space for it to grow. In this blog, we'll introduce you to this fine native tree species, assess which conditions it may grow best under, and give you an idea of just how much space you'll need for it to be successful in your yard.

The Western Hemlock's scientific name is Tsuga heterophylla. Tsuga is the Japanese name for the species. Its specific epithet (species name) heterophylla refers to variability that exists in the length of its needles. The Western Hemlock is usually characterized by its different-sized needles in flat sprays. It also has feathery, flat sprays of foliage that are green on top and whitish underneath.

Native Americans used the Western Hemlock for dye, food, and medicine. They also used the species to tan hides. Additionally, the Western Hemlock was used to fashion small implements, to ward off evil spirits, and to make articles of clothing.

In the early days of the Pacific Northwest timber industry, the Western Hemlock was considered to be "an economically unimportant conifer" (2). The lumbermen believed that the quality of the wood that the species had to offer was low, much like its eastern North American relative, Tsuga canadensis. However, as they gained experience harvesting the Western Hemlock, they soon learned otherwise. Since then, the species has been put to work in a variety of ways. The wood from the tree is pitch-free, strong, and straight-grained. It saws without producing splinters, and is capable of holding a nail. The Western Hemlock has been found to be an excellent material for flooring, particularly for gymnasiums, because it darkens and hardens as it ages. In addition, the wood absorbs preservatives quite easily, which makes it a good choice for poles, pilings, and railroad ties. Its pulped wood, once reduced to a chemical known as alpha-cellulose, makes high quality paper. It is also a good source of cellulose for cellophane, plastic, and rayon products. With all of these uses, the Western Hemlock is far from being "economically unimportant". If anything, it is one of the most economical trees in our region as the species produces more wood per acre than other forest types, improving its ability to keep up with the demand for all the things that it can be used for.

Seedlings of Western Hemlock generally begin their lives on the decaying wood of stumps in the shade of Douglas Fir trees. They generally start out by growing slowly in the shade. In deep, shaded forests, you will often see hemlock progeny growing in rows along a rotting log. However, the Western Hemlock actually grows much faster in full sunlight when an event takes place that exposes the seedlings to the sun. In fact, the Western Hemlock is generally considered to be "shade tolerant" (3), indicating that it prefers areas that have plenty of sunlight. However, it is worth noting that the species also does quite well in shaded areas. The Western Hemlock grows best in moist, cool conditions. The soil should be well drained and have large amounts of organic matter in it. The species does especially well in places that receive more than sixty inches (five feet) of rain per year.

Western Hemlocks produce small cones that are roughly an inch in length. The cones are purplish-green in color when they are young. The cones typically begin maturing in August. The seeds inside the cones are fully ripe by the end of September. However, the seeds don't become accessible until October, which is when the cones open.

The Western Hemlock takes on a pendulous and pyramidal shape, and has graceful branches that sweep in a downward direction. The tree typically blooms in the spring, with mid-April being the most common time. In higher elevations, the bloom period can be later in the season. In southern coastal areas (i.e. Northwest California and Southwest Oregon), the bloom period can be earlier in the season.

By tree standards, Western Hemlocks don't tend to live that long. You will be hard pressed to find one in lowland areas that is 300 years old. However, in higher elevations, trees that fare older than that are known to exist. Most Western Hemlocks die at an earlier age due to stem or root rot fungi, insect damage, and being blown down by the wind.

The Western Hemlock can be found along the Pacific Coast from southeast Alaska to northwest California. You can also find it in the Puget Sound Lowlands, the coastal ranges in both Washington and Oregon, and in the mountains of British Columbia, Idaho, Oregon, and Washington.

Depending on the amount of space you have in your yard, the Western Hemlock may or may not be a good addition. You need to leave plenty of room for it to grow and develop. In the wild, the Western Hemlock can grow to heights of 150 to 195 feet. If you have a lot of acreage, you might be okay with having a tree that tall. If you don't have a lot of acreage, a tree that could be as tall as a 24 story building is probably not a good idea. With that being said, it is worth noting that, from a gardening perspective, a mature Western Hemlock may only reach heights of 80 feet, which is probably still too tall for most yards. I recommend consulting with your local nursery or arborist for advice on how to keep your Western Hemlock from getting too tall.

In addition to being tall, the Western Hemlock is also a wide tree. A mature tree can spread out for up to 20 feet in all directions. Therefore, it is vital that you allow enough space in your yard for the tree to spread so that it doesn't get too close to your house, utility lines, driveways, etc. For example, in Seattle, the city government has outlined the following minimum distances for how far the tree should be planted away from things:

• 15 feet from house or building (1)
• 3 ½ feet back from the face of the curb (1)
• 5 feet from underground utility lines (1)
• 10 feet from power poles (1)
• 7 ½ feet from driveways (10 feet recommended) (1)
• 20 feet from street lights and other existing trees (1)
• 30 feet from street intersections (1)

Before planting the Western Hemlock in your yard, I strongly recommend that you check with your local governing jurisdiction for any minimum distances that they require as they may differ from those presented here.

Another consideration you should take into account when deciding whether or not to plant a Western Hemlock in your yard is how the tree is used by our region's abundant wildlife. If you like watching birds, planting the Western Hemlock could bring some to your yard as it is favorite nesting tree for many bird species. However, if you don't like it when deer or elk eat your plants, you would be better off not planting this tree as they like to eat its foliage and twigs.

References

1. https://www.seattle.gov/trees/planting-and-care/trees-for-neighborhoods/past-plantings/western-hemlock
2. https://www.oregonencyclopedia.org/articles/western_hemlock/#.YYSQqmDMLDc
3. http://www.pnwplants.wsu.edu/PlantDisplay.aspx?PlantID=473
4. http://nativeplantspnw.com/western-hemlock-tsuga-heterophylla/

© Ian D. Caldwell, November 2021