American Black Walnut is probably the most famous and unique species of all our hardwoods.  Because large defect-free trees of exceptionally good form were once common, the wood became prized for furniture, paneling, novelties, and many other items.  The wood was abundant and had a natural resistance to decay, so it was also commonly used for construction purposes such as barn timbers.  Even as late as the 1960's, I saw wal­nut 1 x 12's sold for hay-rack boards because it wouldn't rot.

By the 1970's the wood became relatively expensive, forcing the furniture and cabinet industry to promote other species.  The mid-1990's trend toward light-colored hardwoods also lessened walnut's popularity.  Today, walnut is preferred in office furniture, architectural millwork, high-end gunstocks, specialty and custom items.  While some suppliers feel walnut is once again gaining popularity, walnut lumber currently constitutes less than two percent of all hardwood lumber produced.

Growth and Range

The natural range of black walnut is from the East Coast to the Great Plains, and from Texas and Georgia north to central Minnesota, Wisconsin, Michigan and southern Ontario.  Most of the best quality trees are found in the Central States region from Ohio to Iowa.  The tree has also been widely planted in the Northwest.  This species prefers deep, rich, moist soils of alluvial origin.  The best trees are frequently found on flood-free ledges, just above stream banks.  Walnut will live on poorer soils, but growth is slow and the wood quality is generally poor.  Many walnut plantations have failed to perform well due to the trees being planted on the wrong sites.

Walnut is seldom found in pure stands.  The best trees usually occur sporadically and in association with yellow poplar, white ash, cherry, basswood, beech, and hickory.  A walnut tree can easily reach 70 to 90 feet in height and two to three feet in diameter.  A maximum height of 150 feet and eight feet in diameter has been reported, although large trees are now rare.  Black walnut, butternut, and the hickories are in the same botanical family and closely related.  Four other minor walnut species occur in California, Texas, and Arizona; none of these are important for commercial lumber production

Quality and Color

Walnut's quality can vary greatly by site and geographic location, with several factors affecting a single tree's quality.  First, look to the walnut's bark for clues to the characteristics of the potential wood quality inside.  Deeply furrowed outer bark with an orangish inner bark color indicates a healthy, vigorous tree, but may also signal the presence of undesired excessive sapwood.  A blocky or patchy bark indicates a slow-growing tree, often located on a poor site, containing soft textured wood with a reddish color.

Pine knots can be common in walnut and are often difficult to detect in standing trees.  As they are most easily found as sharp spikes of wood on the trunk surface after the bark is stripped off, pine knots are particularly troublesome to buyers of trees and logs for veneer.

Worm holes and their associated stain are another difficult characteristic to detect in standing trees.  Since log buyers have learned that worms are more prevalent in certain parts of the walnut range, they tend not to concentrate their purchasing efforts in these regions where warmer climates provide for a longer `insect' season.  Although a number of insects or larvae feed on walnut, only a few cause damage, with most of this damage occurring during the sapling stage.

Bird peck is an additional problem that may occur in walnut, although it's more prevalent in other hardwoods. Yellow-bellied sapsuckers probably cause most of the bird peck in walnut.  It is generally believed that the bird pecks a hole to cause the flow of sap.  Insects are attracted to the sap, which the bird then feeds on.  Bird peck in walnut may also indicate the presence of worms.  If the bird peck holes are open, the peck did not reach the cam­bium layer, and no damage to the wood is likely.  However, if callus tissue is located in the peck hole, the hole is said to be "occluded" and a peck mark will show up in the wood beneath the surface.

Walnut's heartwood color and uniformity of color (especially in veneer-quality trees) is an important factor that varies greatly, especially by location.  When first cut, the best colored walnut is light greenish or mint color.  As the wood is exposed to the air it turns a gray-brown color, considered ideal on the market.  Unfortunately, the color can vary, or it can lack uniformity, resulting in dark or splotchy walnut, known as `muddy walnut'.  The color of walnut can also be affected by manufacturing variables such as cooking schedules for veneer flitches and processing time before drying.  Some walnut has `flash' or `flare' in the grain pattern.  Although small quantities of this material are generally not preferred by stock furniture manufacturers or veneer producers because it doesn't mix well with the straight-grained wood, both lumber and veneer of this kind can be prized for custom-type jobs.  Large figured logs capable of paneling large rooms can be valuable as veneer. 

The term `texture' describes a walnut tree's growth rate.  A fast growth rate results in a coarse-textured and somewhat harder wood, while a slow growth rate gives a finer texture and softer wood.  Texture is particularly important in veneer quality trees where a growth rate of eight to nine rings per inch is usually preferred. 

Sapwood, the light-colored band of wood on the outside of a walnut cross section, is considered a defect in veneer because most of it must be clipped off and discarded.  Fast-growth trees tend to have a wider sapwood zone than slow­growth trees.  In lumber, the wood is steamed to darken the sapwood.  If the lumber is not steamed, sapwood is also considered a lumber grading defect by NHLA rules. 

Physical Characteristics

 Walnut is moderately heavy and hard with good strength characteristics.  It machines well and is reasonably easy to dry. The wood has moderate shrinkage.  When finished, the wood has a lustrous rich appearance.

Its rich, brown, lustrous heartwood has a grain pattern and pore size between that of the grainy hardwoods, such as oak, and the uniform textured woods, such as maple and yellow poplar.

In comparison to the trees available today, large old growth trees frequently formed burls and also had large swellings at the butts of the trees.  Both the lumber and the butts, as well as large crotches, were cut for highly decorative veneer.  Some production of burls from grafted English walnut orchards still exists today.

Lumber

Most walnut lumber is priced and sold on the report for the Appalachian Market Region.  The wholesale price (from Weekly Hardwood Review) for green truck­load quantities has been ranging from $200 per thousand board feet to about $1400 per thousand board feet for the best grade.  Woodshop News reports that steamed, kiln dried, 4/4 FAS, surfaced two faces is bringing from $2,500 to $3,100 for thousand board feet quantities, and $4,500 to $6,000 per thousand board feet for quantities of 100 feet at retail outlets east of the Great Plains.

Because of walnut's long-standing reputation as being valuable, the trees are often perceived as having high value.  In today's lumber market, however, both cherry and white hard maple are much more valuable and in greater demand than walnut.  Number 1 and Number 2 Common red oak lumber are also more valuable than walnut.  In fact, the lowest grade of walnut lumber (No. 2A Common) is valued about the same as pallet lumber!

Buyers and sellers should be aware that the National Hardwood Lumber Grades for walnut and butternut are distinctly different than the standard grades that generally apply with slight modifications to other species.  Short lengths are accepted in the top grades of walnut.  Some short boards are graded by counting defects (called standard defects) rather than measuring clear cutting areas.  Minimum board widths for the top grade are narrower and the sizes of cuttings are smaller.  As a result, any one grade in walnut will appear to be of lower quality when compared to lumber graded by the "standard rules".

Because walnut was such a valuable and in-demand species for so long, it's probably the most studied and researched hardwood species in North America.  Scores of articles have been published and genetically superior stock has been offered.  Substantial efforts at planting walnut and caring for plantations have also been put forth.

AMERICAN BLACK WALNUT
LUMBER WEIGHTS

Green black walnut lumber 4,800 lbs./1,000 bd. ft. (58 lbs./cubic ft.)
Air-dried lumber at 15% moisture content 3,200 lbs./1,000 bd. ft.
Kiln-dried lumber at 6% moisture 3,150 lbs./1,000 bd. ft.

AMERICAN BLACK WALNUT
LOG WEIGHTS

Weight of logs per 1,000 bd. ft. (Doyle scale)
24-inch diameter logs = 7,100 lbs.
18-inch diameter logs = 8,300 lbs.
12-inch diameter logs = 11,900 lbs.

Note: It takes a larger quantity of small logs than large logs to equal the same amount of board footage, resulting in more weight far the larger number of small logs.