049 Eastern Hemlock - The Giant of the Cool Forest

Know Your Woods Series

Walk into a mature stand of eastern hemlock and the forest changes.

The canopy becomes darker. The air often feels cooler. The forest floor is shaded and quiet, and enormous trunks can rise overhead from trees that may have been growing for centuries.

Eastern hemlock is one of the great trees of northeastern North America.

It is also an important lumber species — although anyone who has worked much hemlock knows that the wood has a personality all its own.

Welcome to another installment of Know Your Woods.

What Is Eastern Hemlock?

Eastern hemlock is a conifer with the scientific name Tsuga canadensis.

It is sometimes called Canada hemlock or hemlock spruce, although it is neither a true fir nor a spruce.

Eastern hemlock is native to a broad area of eastern North America, including New York, Pennsylvania, New England, the Great Lakes region, southeastern Canada, and portions of the Appalachian Mountains extending southward.

How Prevalent Is Eastern Hemlock?

Eastern hemlock is an important and widespread tree throughout much of the Northeast.

It is particularly associated with cool, moist forests, ravines, stream valleys, north-facing slopes, and other locations where moisture remains relatively dependable.

In New York and Pennsylvania it has historically been an important component of both pure hemlock stands and mixed forests containing species such as eastern white pine, yellow birch, maple, beech, and spruce.

Unlike balsam fir, which becomes increasingly associated with northern forests and higher elevations, eastern hemlock is very much at home throughout large portions of New York and Pennsylvania.

A Tree That Can Become Enormous

Eastern hemlock can become a genuinely impressive tree.

Mature trees commonly reach substantial heights and diameters, and exceptional specimens can become giants.

They are also remarkably long-lived.

Eastern hemlocks can survive for many centuries, with exceptionally old trees reaching ages approaching 800 years or more.

That combination of size and longevity made hemlock an enormous timber resource for generations of northeastern builders and sawmills.

The Shade Champion

One of the most remarkable characteristics of eastern hemlock has nothing to do with its lumber.

It is extraordinarily shade tolerant.

Young hemlocks can survive for decades beneath an established forest canopy while growing extremely slowly.

When an opening eventually develops above them, those suppressed trees can respond and begin growing more rapidly.

This ability helps explain how hemlock can maintain itself beneath a mature forest in conditions where many other tree species would disappear.

A Hemlock Forest Creates Its Own Environment

A dense stand of eastern hemlock changes the environment beneath it.

The thick evergreen canopy intercepts sunlight throughout the year. The forest floor remains heavily shaded, temperatures are moderated, and moisture can be retained differently than in nearby deciduous woods.

The result is a distinctive forest habitat.

Hemlock stands provide important winter shelter for deer and habitat for many other animals. Streams flowing through hemlock forests also benefit from the shade provided by the evergreen canopy.

What Does Eastern Hemlock Wood Look Like?

Eastern hemlock heartwood is generally pale brown, sometimes with a reddish cast. The sapwood tends to be somewhat lighter but is not always sharply separated from the heartwood.

The grain can be relatively straight, but the texture is often coarse and uneven.

Hemlock usually does not have the refined appearance of cherry, walnut, maple, or clear white pine.

It is a more rugged-looking wood — and in many applications, that is part of its appeal.

Working With Hemlock

Hemlock can test a woodworker's patience.

The wood has a tendency to splinter, and those splinters can be long, sharp, and surprisingly stubborn.

Boards can also contain knots, grain irregularities, shake, and areas that behave differently as they pass through woodworking machinery.

Sharp blades and cutters help, but even then hemlock can remind you that wood is a natural material rather than a manufactured product.

For someone accustomed to working with eastern white pine, switching to hemlock can be quite noticeable.

Hemlock at the Sawmill

Hemlock is an interesting wood to watch being sawn because a log that appears perfectly usable from the outside can contain surprises.

Older trees may develop ring shake, where separation occurs along or near the annual growth rings.

Internal stresses, knots, decay, and other defects can also influence how much usable lumber comes from a log.

That is one of the lessons of working at a sawmill: the outside of a log only tells part of the story.

The real story appears one board at a time as the saw works its way through the tree.

How Strong Is Hemlock?

Eastern hemlock is moderately lightweight and moderately hard, but it is not considered an exceptionally strong wood compared with some other structural softwoods.

Its tendency to split and splinter also affects how it behaves during construction.

Despite those limitations, enormous quantities of hemlock have been successfully used in buildings.

Wood does not need to be perfect to be useful. It needs to be appropriate for the job.

Traditional Uses of Eastern Hemlock

Hemlock has historically been used for a wide variety of practical applications, including:

• Framing lumber
• Sheathing
• Roof boards
• Subflooring
• Barns and agricultural buildings
• Timbers
• Boxes and crates
• Pallets
• General construction lumber
• Pulp and paper

Hemlock was often the kind of wood used where builders needed a lot of lumber rather than a flawless piece of furniture wood.

Hemlock in My Woodshop

I have a particularly good example of eastern hemlock as a building material right in my own woodshop.

The walls and ceiling are covered with tongue-and-groove hemlock. Rather than hiding the wood behind drywall, the hemlock itself became the finished interior surface.

The floor provides an interesting contrast. It is tongue-and-groove yellow pine, a harder and more wear-resistant wood better suited to the punishment a workshop floor receives.

That combination illustrates an important lesson in woodworking and construction: there isn't necessarily one "best" wood for a building. A good builder chooses different species according to what each part of the structure needs to do.

The Bark Was Once Almost as Important as the Wood

Eastern hemlock played an enormous role in another nineteenth-century industry: leather tanning.

Hemlock bark contains large quantities of tannins.

Those tannins were extracted and used to convert animal hides into leather.

Entire industries developed around harvesting hemlock bark.

Unfortunately, the bark could become more valuable than the lumber itself. In some areas trees were felled primarily for their bark, with the logs sometimes receiving far less attention than we would expect from such a valuable timber resource today.

Hemlock in Historic Buildings

For anyone investigating an old house, barn, mill, or outbuilding in New York or Pennsylvania, eastern hemlock should always be considered as a possible building wood.

Its abundance and large size made it readily available to nineteenth-century builders.

It was especially practical for structural and utilitarian applications where appearance was secondary.

Finding hemlock in an old building in this region would therefore be completely unsurprising.

Is Hemlock Good Outdoors?

Eastern hemlock is not naturally highly resistant to decay.

Constant exposure to moisture or ground contact can shorten its life considerably.

Yet old hemlock can survive for generations when construction keeps it reasonably dry.

This is another reminder that the durability of wood depends on more than species.

Good building design is one of the best wood preservatives ever invented.

Keep water away, allow wood to dry, protect vulnerable end grain, and even moderately decay-resistant woods can provide remarkably long service.

A Serious Threat to Eastern Hemlock

Today, eastern hemlock faces a threat that has nothing to do with sawmills.

Hemlock woolly adelgid is a tiny invasive insect that feeds on hemlock trees.

Infestations can often be recognized by small white, wool-like masses near the bases of the needles.

As the insects feed, the tree gradually loses vigor. Needles and branches decline, the canopy thins, and heavily affected trees can eventually die.

The loss is much greater than simply losing an individual species of tree.

When mature hemlocks disappear, the entire forest environment can change.

Watching the Change in New York

This isn't merely something described in forestry reports.

In the Waverly, New York area, I have watched eastern hemlocks decline, and it is sad to see.

Farther north, on my parents' land around Jordan Falls in the Adirondack region, the hemlocks have remained in much better condition.

That contrast makes the threat particularly noticeable.

Conditions can vary substantially from one area to another. Cold winter temperatures can reduce populations of hemlock woolly adelgid, while climate, elevation, terrain, and local conditions can influence how the insect spreads and survives.

It is something worth watching carefully in the years ahead.

Why Losing Hemlock Matters

If eastern hemlock were simply replaced by another tree, its decline would still be unfortunate.

But forests do not work that way.

A mature hemlock creates deep shade, intercepts snow, moderates temperatures, influences the forest floor, and provides habitat for wildlife.

Remove enough hemlocks and more sunlight reaches the ground. Temperatures change. Other plants become established. Streams that once flowed beneath dense evergreen shade can receive more sunlight.

The loss of a tree can eventually become the transformation of an ecosystem.

A Woodworker's Tree and a Forest Tree

It is easy for woodworkers to think about trees primarily in terms of boards.

How does it saw?

How does it plane?

Does it split?

Will it hold a nail?

What can we build from it?

Those are worthwhile questions.

But learning about wood eventually leads us back to the forest.

Eastern hemlock reminds us that the material stacked in a lumber pile began as part of a much larger living system.

Know Your Woods

Eastern hemlock may never be the easiest wood in the shop.

It splinters. It can contain shake. It isn't exceptionally decay resistant. It can be coarse and unpredictable.

Yet for generations it helped build houses, barns, mills, roofs, floors, crates, and communities throughout the Northeast.

And standing in the forest, an old eastern hemlock is something much greater than a future stack of lumber.

It is one of the giants of the eastern woods.

Understanding the wood makes us better woodworkers. Understanding the tree makes us better caretakers of the forest.