044 Willow: A Soft Hardwood Built to Bend

Know Your Woods: The Softer Eastern Hardwoods Series

Willow is one of those trees almost everyone recognizes in some form.

We associate willows with streams, riverbanks, wetlands, flexible branches, and rapidly growing trees leaning toward the water.

But willow as lumber is something many woodworkers know much less about.

That makes it a particularly interesting addition to our Know Your Woods series.

Like basswood, aspen, yellow-poplar, and cucumbertree, willow is a hardwood botanically—but its wood is relatively soft and lightweight.

And willow introduces another characteristic that hardness numbers alone cannot adequately describe:

Flexibility.

Which Willow Are We Talking About?

There are many species of willow in North America, ranging from small shrubs to substantial trees.

For eastern North American lumber, the species of greatest importance is generally black willow (Salix nigra).

Black willow is the largest and most commercially important native willow in North America.

Other willows may occasionally become lumber, especially when locally harvested, but black willow gives us the best species for understanding willow as an eastern hardwood.

A Tree That Loves Water

If someone tells you a large willow log came from beside a river, creek, pond, or wet bottomland, the location itself is already an identification clue.

Black willow strongly favors wet ground.

It commonly grows along:

• streambanks,
• riverbanks,
• lake margins,
• wet bottomlands,
• floodplains,
• and other areas where moisture is plentiful.

It tolerates flooding remarkably well and is an important pioneer species on newly deposited, wet soils.

This is another lesson in identifying wood: sometimes knowing where the tree grew can be almost as useful as looking at the board.

Identifying Black Willow as a Tree

Black willow usually has long, narrow leaves with finely toothed margins.

The leaves are much narrower than those of basswood, yellow-poplar, or cucumbertree and give the tree a characteristic fine-textured appearance.

Older black willow develops dark, deeply furrowed bark.

The tree often has an irregular form, particularly compared with the tall, straight trunks we may associate with yellow-poplar.

Willow is a fast-growing tree, and under good conditions black willow can become surprisingly large.

Once that tree becomes a debarked log or pile of lumber, however, we lose most of those easy clues.

Then we have to learn the wood.

Identifying Willow Lumber

Black willow lumber generally has pale sapwood and light reddish-brown, grayish-brown, or tan heartwood.

The grain is often straight, but it can also be irregular or interlocked.

That irregular grain can become important when machining the wood.

When trying to identify willow lumber, I would look for a combination of:

• Color: Pale sapwood with tan, grayish-brown, or light reddish-brown heartwood.
• Weight: Lightweight for a hardwood.
• Hardness: Relatively soft.
• Grain: Straight to irregular or interlocked.
• Texture: Fine to medium and generally even.
• Pores: Small and diffuse rather than arranged in the obvious bands seen in oak or ash.
• Workability: Generally easy to cut, although irregular grain and soft fibers can affect the finished surface.

Willow is another diffuse-porous hardwood, putting it structurally into familiar territory with several of the woods we've already examined.

How Hard Is Willow?

Black willow has a Janka hardness of approximately 570 pounds-force.

That may be harder than someone expecting an extremely soft wood might guess.

Let's add it to our growing comparison:

• Quaking Aspen: approximately 350 lbf
• Basswood: approximately 410 lbf
• Bigtooth Aspen: approximately 420 lbf
• Yellow-Poplar: approximately 540 lbf
• Cucumbertree: approximately 550 lbf
• Black Willow: approximately 570 lbf

Willow now sits near the upper end of our softer-hardwood group.

But compare it with northern red oak at approximately 1,290 lbf, sugar maple around 1,450 lbf, or hickory approaching or exceeding 1,800 lbf, and willow's place among the softer hardwoods becomes much clearer.

Lightweight Lumber

Black willow is also relatively light, averaging roughly 26 pounds per cubic foot when dried.

That puts it surprisingly close to basswood and quaking aspen in weight.

Our hands therefore give us another clue.

If an unknown eastern hardwood board is substantially lighter than expected for its size, we can begin narrowing the possibilities.

It could be basswood.

It could be aspen.

It could be willow.

Then we start looking for the characteristics that separate them.

Soft Wood Doesn't Always Mean Clean Cutting

Our Aspen article taught us an important lesson: a soft wood can still behave unexpectedly under a cutting edge.

Willow reinforces that lesson.

Because the wood is relatively soft and may have irregular or interlocked grain, machining can sometimes produce fuzzy or torn surfaces rather than the extremely clean cuts associated with good basswood.

Sharp tools become particularly important.

A dull cutting edge may compress or pull fibers rather than severing them cleanly.

Once again, the Janka hardness number tells us only part of the story.

Willow and Flexibility

One of willow's defining characteristics isn't really about hardness at all.

It is the tree's ability to bend.

Anyone who has handled young willow branches has probably experienced this. Thin willow stems can flex dramatically without immediately snapping.

This characteristic has been used by people for thousands of years.

Flexible willow shoots have been woven into baskets, fences, traps, furniture, containers, and many other useful objects.

This gives us another way of thinking about wood properties.

Hardness measures resistance to indentation.

Strength measures something different.

Stiffness measures something different again.

And flexibility is another characteristic altogether.

A wood can be relatively soft yet remarkably useful because it bends instead of breaking.

Willow and Basketry

Willow has one of the longest histories of any wood used for weaving.

Young shoots can be harvested, prepared, and woven while flexible.

Traditional willow basketry developed in many cultures because the material combines several valuable properties:

• rapid growth,
• long slender shoots,
• flexibility,
• light weight,
• and widespread availability near water.

Instead of sawing the tree into boards, people could use the natural form of the young stems themselves.

That is an entirely different way of working with wood.

Willow as Lumber

Black willow has been used for a variety of practical products, including:

• furniture components,
• boxes and crates,
• interior woodwork,
• pallets and utility lumber,
• veneer,
• turned objects,
• carvings,
• woodenware,
• and pulp and fiber products.

Its low weight can be an advantage wherever a heavy hardwood is unnecessary.

Like several other species in this series, willow is often more valuable as a practical working material than as a prestige furniture wood.

What About Carving Willow?

Willow can certainly be carved.

At approximately 570 lbf on the Janka scale, it remains relatively soft, and sharp hand tools can remove material without the effort required for oak, hard maple, or hickory.

But again we return to grain structure.

Irregular or interlocked grain may make fine detail less predictable than it is in basswood.

For larger shapes, rustic carvings, bowls, spoons, and less intricate work, willow can be quite usable.

For extremely fine detail, basswood's uniform structure still gives it an advantage.

Willow and Oil Finishes

Oil generally warms willow's pale tan and brown coloration and makes the grain somewhat more apparent.

Because willow normally lacks the dramatic figure of walnut or curly maple, the effect may be relatively subtle.

Irregular grain can sometimes create more interesting visual movement than expected, however.

As with every species in this series, a test piece is worthwhile.

One of the things I increasingly enjoy about finishing wood is watching how dramatically some species change while others simply become a warmer, richer version of themselves.

Drying Willow

Fresh willow can contain a considerable amount of moisture.

That shouldn't be surprising when we consider where the tree likes to grow.

Careful drying is important because willow can shrink, distort, or develop defects if moisture is removed too rapidly or unevenly.

Proper stacking, stickers, airflow, and protection from excessively rapid drying become important.

For someone working around a sawmill, green weight can also become another useful observation.

A freshly sawn willow board and the same board after thorough air drying can feel like surprisingly different pieces of wood.

Willow and Water: A Fascinating Relationship

Willow loves water while it is alive.

That does not mean willow lumber is naturally durable when exposed to moisture.

This distinction is important.

A tree's ability to thrive in wet soil does not automatically mean its dead wood is resistant to decay.

Black willow has relatively poor natural decay resistance.

Once converted into lumber, it is generally better suited to protected applications unless properly treated or otherwise protected.

This is a great example of why we should never assume that the environment a living tree prefers tells us how its lumber will perform after the tree is cut.

Fast Growth and Disturbed Ground

Like aspen and cottonwood, willow is good at taking advantage of opportunity.

Black willow can quickly colonize wet, disturbed soils along streams, rivers, sandbars, and floodplains.

Seeds can establish rapidly when they reach suitable moist ground.

This makes willow an important pioneer species.

Its roots can also help stabilize soil along waterways, reducing erosion and helping establish vegetation on newly disturbed ground.

Again, we find that a species sometimes considered ordinary has an important job in the landscape.

Willow and Wildlife

Willows provide food and habitat for many forms of wildlife.

Young shoots, leaves, bark, buds, and twigs can be browsed by mammals, while willow thickets provide valuable cover and nesting habitat for birds.

The flowers appear in catkins and provide early-season resources for insects.

Willow's ecological importance extends well beyond its usefulness as lumber.

Willow Has Separate Male and Female Trees

Another interesting characteristic of willows is that individual trees are generally either male or female.

This is called being dioecious.

Male trees produce male flowers, while female trees produce female flowers.

The flowers occur in catkins rather than the showy blossoms we saw with yellow-poplar or the unusual flowers of cucumbertree.

The female trees eventually produce large numbers of tiny seeds associated with cottony fibers that help them disperse.

That feature gives us a nice preview of our next wood: cottonwood.

Aspen, Willow, and Cottonwood: We're Finding a Pattern

As we move through these species, an ecological pattern is beginning to appear.

Aspen rapidly occupies disturbed land.

Willow rapidly occupies wet disturbed land.

Cottonwood, which we'll explore next, is another fast-growing pioneer strongly associated with rivers and floodplains.

These softer hardwoods aren't simply trees that happen to produce lightweight lumber.

Many are specialists in growing quickly, exploiting newly available sunlight, and establishing forests or woody cover where conditions have recently changed.

Fast growth and relatively lightweight wood often go together.

That relationship is worth remembering.

Identifying Willow at the Sawmill

Suppose we're standing in front of an unidentified pile of pale, lightweight hardwood lumber.

What might make us consider willow?

First, the lumber is light.

The heartwood may have more tan, grayish, or reddish-brown coloration than very pale aspen or basswood.

The grain may be less perfectly straight and uniform than basswood.

Irregular or interlocked grain may appear.

The wood is relatively soft but not exceptionally so.

Machined surfaces may show some fuzzy or torn grain.

And if we know the logs came from wet bottomland or beside a stream, that becomes another useful piece of evidence.

No single clue proves willow.

But several clues pointing in the same direction make the identification increasingly convincing.

Our Softer Eastern Hardwoods Comparison

Our mental identification library continues to grow:

• Basswood: about 410 lbf; approximately 26 lb/ft³; pale and fine textured; outstanding carving wood; I've noticed freshly cut lumber becoming more yellow-brown after exposure.
• Quaking Aspen: about 350 lbf; approximately 26 lb/ft³; extremely soft and pale; some freshly cut boards can produce remarkable masses of fuzzy fibers when planed.
• Bigtooth Aspen: about 420 lbf; lightweight and soft; closely related to quaking aspen and often grouped with it as lumber.
• Yellow-Poplar: about 540 lbf; approximately 29 lb/ft³; easy working; cream through brown with characteristic green or olive coloration sometimes present.
• Cucumbertree: about 550 lbf; approximately 30 lb/ft³; closely related to yellow-poplar; I've noticed light green and occasional purplish coloration in freshly cut lumber.
• Black Willow: about 570 lbf; approximately 26 lb/ft³; lightweight, flexible, sometimes irregular grained, and strongly associated with wet ground.

Looking at those numbers reveals something interesting.

Weight and hardness don't necessarily move together.

Black willow can weigh approximately the same as basswood and quaking aspen while being noticeably harder according to the Janka test.

That's another reason identifying wood requires more than picking it up or pressing a fingernail into it.

A Wood Designed for Its Environment

Willow makes more sense when we stop judging it against oak, walnut, or maple and instead ask what the tree is designed to do.

It grows quickly.

It colonizes wet disturbed ground.

Its young stems bend.

Its roots help hold soil.

It provides wildlife habitat.

People have woven its flexible shoots for thousands of years.

And when the tree becomes lumber, it gives us a lightweight, relatively soft material that is easy to work for the right applications.

Willow doesn't need to behave like oak.

Its value comes from behaving like willow.

Understanding wood becomes much easier when we stop asking whether a species is "good" or "bad" and start asking what that tree was naturally built to do.