Utilization of American Black Walnut Plantation Thinnings
By Daniel Cassens and Lenny Farlee


American Black Walnut (Juglans nigra L.) is North America’s most valuable commercial hardwood species. It is highly prized in the domestic and international markets for fine face veneer and lumber. These two products are the raw material for the furniture, cabinet, architectural millwork, flooring and paneling industries.

The species is wide ranging from the East coast to the Great Plains and from southern Minnesota and Michigan to the southern coastal plain. However, from a commercial perspective, the highest quality material, especially for veneer, is found in the northern Corn Belt region. The species accounts for only about two percent of all the hardwood lumber cut.

Because of its economic and aesthetic value for lumber and veneer, and the potential for nut production the species has been widely planted. Early settlers on prairie regions east of the Mississippi River were noted to have planted trees prior to the Civil War. The Timber Culture Act (1873) encouraged tree planting on the western planes. Walnut was undoubtedly a significant species. By the 1960’s planting walnut plantations was not uncommon. Plantation establishment continued with the Conservation Reserve Program. The number of acres in Walnut plantations is not known. Considerable research on genetic improvement has been done and continues.

The heartwood of walnut is a beautiful chocolate brown but the sapwood is white. The sapwood can stain to a grey color in the log or during lumber drying. The industry steams green walnut lumber at about 230 degrees Fahrenheit which darkens the sapwood but it can still be distinguished. Steaming also reportedly makes the heartwood color more uniform. The commercial industry prefers a more uniform product but some individuals and custom woodworkers prefer the more natural and variable color of un-steamed walnut. Actively managed plantation trees are typically fast-growing and contain wide bands of sapwood. Landscape trees and even some vigorous timber trees can have a sapwood band of two inches or more. It is not uncommon for the commercial industry to sort pieces with a high sapwood content and market them at a reduced price.

The development of small, thin kerf, portable band mills over the last 25 years is a factor which could contribute to the utilization of plantation thinnings. Compared to heavy duty and expensive traditional band and circle mills, these newer relatively inexpensive mills are now common place, are portable, and have a minimum kerf (the thickness of the blade-cut in the wood) yielding more lumber and less sawdust waste.

In plantation establishment, trees are often planted about 8 to 10 feet apart in rows. Figure 1. (above) A 47-year old well cared for walnut plantation at Martell Forest in Tippecanoe County, Indiana. Figure 2. (below) Unmanaged walnut plantation of unknown age.Close spacing of trees in plantations helps develop straight stems through competition between tree crowns. This competition also helps to keep side limbs small and naturally pruned through shading or more easily mechanically pruned to produce clear wood. This close spacing necessitates thinning as tree crowns begin to compete to maintain vigorous growth of the trees to be grown to harvestable size. Unfortunately, these small stems removed in thinnings have no or very little economic value and many landowners are reluctant to thin even though the remaining trees would benefit. Figure 1 shows a 47 year old walnut plantation that has been well cared for and Figure 2 shows a 30 year old plantation in need of thinning.

In an attempt to encourage landowners to appropriately thin walnut plantations and to evaluate the potential use of these thinnings we initiated a study of 6 plantation grown walnut trees ranging in diameter from 9.3 to 18 inches. We are not encouraging the harvesting of small diameter plantation walnut trees other than to improve the growth rate and future value of the remaining trees. Small walnuts with good potential to produce high quality logs may provide good investment returns as they grow in volume and increase in unit value. Cutting quality trees just as they reach marketable size can limit your long-term income potential. Not cutting lower-quality trees competing with your quality trees slows the growth and gain in value of those good trees.

In April of 2016, 6 plantation-grown black walnut trees of various sizes were harvested and milled on a portable band mill to assess the volume, quality and value of lumber that might be recovered in a thinning operation. Five 35-year old trees planted in 1981 by Walt Beineke, were donated by ArborAmerica, Inc. of West Point, IN., and the largest of the six trees came from a 1968 plantation at the Purdue University FNR Martell Forest. The first five trees were Purdue Number One grafts planted on a fairly well drained deep sandy loam soil, considered a good walnut site. Purdue Number One is a walnut tree selected for good timber form and propagated by grafting stem sections from the parent tree onto walnut root stock. There was some overdosing with simazine herbicide during the first six years and one end of the plantation has a high water table which negatively impacted growth. The plantation averages about 12 inches DBH (diameter at 4.5 feet above ground) giving a growth rate of 0.34 inches per year. The plantation was well managed for the first six years followed by no management for 12 years. When Arbor America purchased the property, the plantation was once again managed.1 The sixth and largest tree came from a 47-year old well managed plantation nearly adjacent to the Arbor America property. Table 1 summarizes tree and log data.

The logs were processed using a portable band mill, and the lumber, separated by trees, was sent to Pike Lumber Company, Akron, IN for professional scaling and grading, and comments on marketability. One-half of the lumber was steamed and the rest was left un-steamed for comparison and to explore potential markets for sappy walnut lumber. The lumber was then kiln dried. Indiana Hardwood Specialists of Spencer, IN processed it into flooring and Enviro Finishing of Richmond, IN., applied an environmentally friendly solvent free coating that is cured with UV light.

 For walnut, the rigor of the National Hardwood Lumber Grading rules is substantially reduced compared to the standard grades for other species, providing opportunities for smaller boards to meet higher grade standards. F1F is First and Seconds one face. It is essentially an FAS board (the top grade) on one face and a Number 1 common grade on the back side. These two grades are often combined in the market place and sold for the same price. For walnut graded on a cutting unit basis (the typical method for all hardwood lumber), the board must measure at least 5”x 8’, have minimum clear cuttings at least 4”x 3’ or 3”x 6’ and have a minimum yield of 83.3% clear on one face. Number 1 Common cuttings must measure at least 3” x 3’ or 4”x 2’ and yield at least 66.6% clear. Number 2 common walnut has a minimum clear cutting of 2” or wider containing at least 72 square inches and yield 50%. Most walnut lumber will grade at least 2C. In addition to grading walnut lumber on a cutting unit basis, 6’ and 7’ boards can be graded on a defect basis. In this situation, the size of defects is limited and the number of defects is simply counted. This allows many of these short pieces to be graded FAS. There are additional details about the grades that can be viewed at: http://www.nhla.com/rulesbook. These rules represent the minimum standard that can be advertised by firms using them, but firms may exceed these standards in sorting or grading to meet the needs of customers and prevailing markets.

Table 1 provides size and volume data on the trees and logs as well as the average sapwood radius. Figure 3 shows the excessive sapwood on the five smaller logs and Figure 4 shows the narrower sapwood on the larger log where the 12- foot log was cut. The radius of the sapwood on the butt end for these logs is always greater than at the top. Some of the sapwood on the butt end is likely to be milled off due to taper in butt logs. Also the radius of sapwood on the largest log is less than that for all of the other logs with one exception.

Table 2 shows that the three largest diameter trees, 13.3, 15 and 18 inches DBH, produced 32%, 42%, and 57% F1F and better grade lumber, respectively, which is priced at nearly twice the value of the next lower grade, #1 common. The three smallest trees, 9.3, 10.3 and 11.2 inches DBH, produced 0%, 6.4% and 9.5% F1F and better lumber. Based on the April 15, 2016 Hardwood Market Report the total lumber values are also given.2

The 18 inch DBH tree was 47 years old when processed and the value of the lumber was $376.85. The next largest tree (15 inch DBH) was 34 years old and yielded a lumber value of $192.52 subject to discounting for excess sap. The value of standing timber is usually subject to many variables and therefore hard to estimate. Using the 2015 Indiana Forest Products Price Report we can estimate the value of the two largest trees. Assuming the 18-inch tree had a prime butt log and two Number two logs, the delivered log value is $231.47. Assuming $200.00 to log and haul the value of the standing tree becomes $196.14. Similarly, the 15-inch tree has one Number two log and two Number three logs with a value of $65.07. The value of the standing tree is estimated to be $47.87.

Mill Management indicated the narrow, short, low grade and sappy lumber (Fig. 5) for all but the largest tree could be sold into the Asian market but at just 60% of the value indicated in Table 2. So despite the fact that these boards technically met grade standards, they would not be sold at prevailing domestic values. The larger tree was acceptable at prevailing market values. The company processing the flooring said that the sappy lumber would be usable for their “rustic” grade. In a normal run of steamed Walnut lumber, they separate the boards with heavy sap and market it for very nearly as much money as the non-sappy flooring. The lumber from the large log was typical of current commercial production.

Figure 3. (left) Extensive sapwood of the butt end of the five smaller butt logs.The traditional industry will not have much interest in plantation grown trees until they reach at least 13 inches DBH. Eighteen inch DBH trees are certainly marketable. One landowner has had some success in marketing plantation trees by combining their sale with adjacent traditional timber sales.

These smaller trees will produce lumber that can be used locally or perhaps manufactured into paneling or flooring. Figure 6 shows the appearance of finished flooring for both steamed and unsteamed boards. Some individuals may prefer the white sapwood and heartwood contrast while others would prefer the more uniform appearance. The company that manufactured some of the boards into flooring indicated they had no problem marketing rustic (low grade) sappy walnut. The product can be sold but it is not likely to be an economically viable operation until trees are at least the 15-inch DBH and substantial volumes are available at one site.Figure 4. (right) Narrow sapwood at 12-foot height on larger tree.

Until plantation Walnut trees reach at least a 15 inch DBH, they will not have much commercial value. However, the lumber from these smaller trees can still be useful on a local use basis or because of an intrinsic value. The ultimate objective is to manage these mid aged plantations for maximum growth, quality and value. This will require the removal of smaller, lower quality trees regardless of whether they are used or not. The remaining trees will increase in value and benefit the landowner as well as the wood manufacturing industry.

Figure 5. The five surfaced boards on the right show the range in quality and color of heartwood and sapwood after steaming. The five pieces on the left are unsteamed.Figure 6. Manufactured flooring showing a range of board quality in both natural (left) and steamed lumber.Daniel Cassens is a Professor of Wood Products in the Department of Forestry and Natural Resources at Purdue University. Lenny Farlee is an Extension Forester with the USDA Hardwood Tree Improvement and Regeneration Center located at Purdue University.

1Personal communication with Walt Beneke, W. Lafayette, IN.

2Hardwood Market Report April 15, 2016.