Description
Leaf: Alternate, pinnately compound, with 15-23 leaflets; leaflets up to 3 1/2 inches long and 1 1/2 inches wide, ovate or broadly lance-shaped, pointed at the tip, rounded at the asymmetrical base, toothed along the edges; thin, yellow-green and smooth on the upper surface, paler and hairy on the lower surface turning yellow to chartreuse in the autumn, though fall color may be absent or poor; young leaves emerging later than most others in the spring and autumn leaves falling before most others; crushed leaves especially pungent.
Flower: Male and female flowers on the same tree, appearing in mid- to late spring when the leaves are partly grown; the male flowers several in thick, yellow-green, hairy catkins, drooping from the previous year's twig growth; the smaller female much fewer in small spikes occurring on the current season's stem growth; neither flower type with petals.
Fruit: Borne singly or in pairs, almost spherical, large, 1 1/3 to 3 inches in diameter; the thick husk in one piece, rough-dotted, dull green to yellow-green when immature and yellow-black when ripe; the nutshell very hard, oval, thick, rough-ridged, dark sepia brown; the seed sweet, rich flavored, oily, two lobed above, four lobed below the middle.
Twig: Hairless, stout, greenish or orange-brown, pith light brown and chambered by woody partitions; buds whitish, woolly, more or less rounded at the tip, up to 1/2 inch long; leaf scars large, alternate, without hairy fringe, shield-shaped, elevated, with 3 bundle traces.
Bark: Warm medium to dark brown or black; flaky when young; becoming very rough with deep, short, perpendicular furrows, and rounded, confluent ridges, forming a diamond pattern as the ridges interlace.
Form: Large tree up to 150 feet tall; trunk diameter 2 to 5 feet, often sharply divided; crown broadly rounded and open with heavy alternate branches; trunk straight, columnar, not buttressed at the base.
Discussion
Black walnut wood is one of the most desirable for lumber and veneer. Being hard, heavy, coarse-grained, attractive, and easy to work with, it is used for cabinets, veneers, furniture, interior finishing, and gunstocks. Rural landowners are often approached by buyers wishing to acquire the black walnut trees from their property. Some specimens have been known to be stolen.
The nuts are a food source for humans, squirrels, mice, and other wildlife. Deer eat the twigs.
Walnut bark is a traditional source of yellow-brown dye. Also, Native Americans used black walnut medicinally to treat skin disorders and as a psychological aid.
During World War II, airplane pistons were cleaned with a "nut shell" blaster and this idea was carried into the auto industry; manufacturers used shells to debur precision gears. Ground shell products are also used to clean jet engines, as additives to drilling mud for oil drilling operations, as filler in dynamite, as a non slip agent in automobile tires, as an air-pressured propellant to strip paints, as a filter agent for scrubbers in smokestacks, and as a flourlike carrying agent in various insecticides.
The leaves, bark, nut husks and roots contain "juglone," a chemical that is lethal to and prevents the growth of many other plants within the tree's rooting zone. In the woods, very few other species grow beneath black walnut trees. Tomatoes do not survive near these trees, and the juglone inhibits apples, paper birch, red pine, white pine, and Scotch pine. Bruised walnut husks were once used to kill fish for human consumption, but this practice has been made illegal.
Urban homeowners often prefer to rid their property of black walnut trees because they present a never-ending cycle of clean-up chores. The trees begin dropping leaves as soon as the late-summer drought sets in, and then continue to drop twigs and whole or squirrel-chewed husks and nutshells, staining sidewalks and driveways and getting caught by the lawnmower.
Distinguishing Characteristics
The black walnut is recognized by its characteristic buds, chambered pith, and fruits.
Distribution
Massachusetts across to Minnesota, south to Texas, east to Florida.
Images
Click each small picture to see a larger image.
Location
N 39.29874º W -89.89892º
On the southeast side of Loveless Park, South Locust
Street, Carlinville, Macoupin County, IL.
Copyright
Photos © 2002 Morgan Rathgeb, Carlinville High School, linke@carlinvilleschools.net
Photos © 2002 Carla Maly, Carlinville High School, linke@carlinvilleschools.net
References
George A. Petrides, Tree and Shrubs, 1986, Houghton Mifflin Company.
F. Schuyler Mathews, Field Book of American Trees and Shrubs, 1915, G. P. Putnam's Sons.
Robert H. Mohlenbrock, Forest Trees of Illinois, 1996, Illinois Department of Natural Resources.
Ohio Department of Natural Resources
http://www.dnr.state.oh.us/forestry/Education/ohiotrees/walnutblack.htm
Illinois State Museum
http://www.museum.state.il.us/muslink/forest/htmls/trees/J-nigra.html
Silvics
of North America
http://forestry.about.com/library/silvics/blsiljugnig.htm?terms=black+walnut
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