Nebraska Forest Service


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Black walnut (Juglans nigra L.), within the family Juglandaceae, is a premier hardwood timber species in the United States. Its native range encompasses most of the eastern U.S., roughly extending from eastern South Dakota and eastern Texas on its western edge to Massachusetts and western Florida in the east (Figure 1). The occurrence and productivity of black walnut on the western edge of its native range, including eastern Nebraska, is largely a function of available water during the growing season. However, black walnut has been extensively planted west and north of its native range. Studies have shown black walnut can withstand moving 200 miles northward from its native range without likelihood of cold injury (Bey, 1980). Black walnut is sensitive to soil conditions. It grows best on deep, well-drained, nearly neutral soils that are generally moist and fertile (Williams, 1990). Black walnut grows in many mixed mesophytic forests, but it is seldom abundant (Schlesinger & Funk, 1977). Usually it is found scattered among other tree species. Pure stands are rare, relatively small, and usually located on the edge of its native range (Williams, 1990). Although there is no universal vegetative indicator, the presence of Kentucky coffeetree (Gymnocladus dioicus) seems to indicate a good walnut growing site (Brinkman, 1965). In general, where white ash, red oak, sugar maple, slippery elm, or yellowpoplar grow well, black walnut also thrives. The majority of black walnut trees occur in natural stands. Walnut plantations (ca. 13,800 ac) account for only about 1 percent of the black walnut timber volume harvested in the U.S. each year (Shifley, 2004), even though black walnut has been cultivated since 1686 (Michler, Woeste & Pijut, 2007). Eight states currently have the greatest volume of black walnut growing stock on timberland: Missouri, Ohio, Iowa, Indiana, Illinois, Tennessee, West Virginia, and Michigan (Shifley, 2004). Black walnut is classified as a “shade intolerant” tree. It tends to develop a straight, limb-free trunk when growing as a dominant and/ or co-dominant tree under competition with other forest trees. It typically forms a taproot and wide-spreading lateral roots. The growing season of black walnut ranges from 140 days in the north to 280 days in western Florida. Annual precipitation in its native range varies from less than 25 inches in northern Nebraska to more than 70 inches in the Appalachian Mountains of Tennessee and North Carolina (Williams, 1990). Black walnut is prized for its chocolate- brown, straight-grained wood which is used to make fine furniture, expensive gunstocks, and high-quality veneer products. The nuts of the black walnut are relished as food by humans and animals. Black walnut nutmeats are often used in baked goods (cookies, cakes, etc.) and ice cream products. The healthful nutmeats are low in sugar and saturated fats, high in polyunsaturated and monounsaturated fats, a good source of protein and fiber, and contain no cholesterol (USDA-ARS, 2004). Even the nut shells are made into useful products. During World War II, engine pistons were cleaned with a “nut shell” blaster. Later, the automobile industry used ground black walnut shell to de-burr precision gears (Williams, 1990). Today, ground black walnut shell is used in a variety of products—a soft abrasive to clean jet engines, electronic circuit boards, ship and automobile gear systems, a filler in dynamite, a filter agent for smokestack scrubbers, and in oil drilling.