What Wood Is That?

Field identification guides for living trees offer plenty of tips for telling one species from another. Leaves, bark, overall shape, twigs, and other characteristics give you all the clues needed.

For wood of questionable identity, though, you must rely on a different set of clues. Wood technologists call them "keys." The following basic ones help you identify unfamiliar native hardwoods that you might come across.

Boards accumulate dust, dirt, and a dull patina of oxidation that cloud identification. Create a fresh surface the size of your hand with a cabinet scraper, knife, or razor blade on the tangential surface (the top or bottom of a flatsawn board). This sraping also should give you an idea of the mystery wood's hardness relative to wood you're familiar with. Walnut should be instantly recognizable. So should the pinkish tan of red oak. Grain pattern might ring a bell, too. Broaden your ability by studying the color and grain of wood at your supplier, and as you work different species in the shop.

Wet a fresh surface with a little water or saliva. Doing this "activates" the wood, even if it's old and dry as a bone. Now take a sniff. If it has an odor, does it smell like any wood you've worked in the shop?

No wood smells as medicinal as sassafras. Maple has a distinctive odor, too. And some people think walnut has a nutty smell.

When a strange wood's color, grain, and scent fail to name it, examine its fingerprint. Professionals turn to their microscopes for a close-up look. Yet, a hand lens of 10X magnification, available at jewelry stores and from opticians, lets anyone do practically the same thing. This type of investigation, however, requires a look at a freshly cut section of end grain.

Hardwoods that grow in the earth's temperate (non-tropical) zone display annual growth rings in their wood's end grain. These growth rings have both an earlywood portion and a latewood portion. The wider earlywood reflects the rapid growth of the early season; the narrower latewood, the slower growth of the later season.

Within the earlywood and latewood portions of the grown ring you'll find pores. It's the size of the pores and how they're distributed in the growth rings that classify a hardwood as either ring-porous, diffuse-porous, or semi-ring-porous.

Ring-porous species show a sharp distinction in the size of the pores of the earlywood when compared to those in the latewood portion of the ring. Ash, elm, hickory, red oak, white oak.

Diffuse-porous species show little difference in pore size no matter where they appear in the growth ring. Basswood, red alder, sugar maple, sycamore, yellow birch, yellow poplar.

Semi-ring-porous trees have a gradual change in pore size across the ring. Black cherry, black walnut, pecan, tanoak.

A few genus trees, such as the hickory (Carya), fall into more than one classification. That's because species within the genus—in this case the true hickory, notably shagbark, and pecan, also a hickory—are different in their pore size and growth-ring distribution.

When cells join to form a flat band of tissue that extends horizontally from its origin to the bark, it's called a ray. If the band happens to be several cells tall and wide as well, it's an aggregate ray. When a ray connects to the pith (innermost part of the tree), it becomes a medullary ray.

In commercial timber trees, only beech, the oaks, sycamore, tanoak (not a true oak), and red alder have large, conspicuous rays. In beech, the oaks, and sycamore, you can see them without magnification.

To solve mysteries in wood identification, it helps to have on hand a collection of wood samples that have been positively identified and labeled. Blocks about 3x5" work nicely. Woodworkers Source (800/423-2450) offers a nice collection of 30 such samples, plus the four-color, 60-page Fine Hardwoods Selectorama for $59 ppd.

Wood identification requires some study. If you want to get really serious about it, here's a good book to help you out: Identifying Wood—Accurate Results with Simple Tools, by R. Bruce Hoadly, The Taunton Press Inc., Newton, Conn., 1990, about $40.

It's suppose that your unidentified wood has a plainsawn grain pattern that looks much like red oak, and seems just as hard and heavy. It has no scent and lacks aroma as well as the hint of pink normally common to red oak.

With a hand lens, you see that your mystery wood's growth rings have the tell-tale signs of a ring-porous species. Rays aren't evident, though, so you dismiss the notion that it's an oak. It's also not as hard, heavy, or brown enough to be a hickory.

How about elm? Not likely because your sample doesn't have an odor, and its grain still reminds you of red oak. From the list, you've eliminated all candidates except ash. It could be that; but white ash or black? With the hand lens, you look at the end grain again. Your wood has large earlywood pores and wide growth wings. You've read that black ash usually grows slowly in damp, cool conditions. That means its growth rings would be narrower. So white ash is your answer.