Appendices & Glossary - Botanical Research Institute of Texas

1312 APPENDIX TWENTY-ONE/COMMERCIALLY IMPORTANT TIMBER TREES OF EAST TEXAS
JUGLANS NIGRA L. BLACK WALNUT
(JUGLANDACEAE, WALNUT FAMILY)
Other Common Names: EASTERN BLACK WALNUT, AMERICAN BLACK WALNUT, AMERICAN WALNUT
Form and Size: large tree, 30–40 m tall, rarely to 50 m; trunk straight for about half its height, to 2 m in diameter; the
crown open and rounded at the top.
Leaves: deciduous, alternate, pinnately (=feather-like) compound, composed of (9–)15–19(–23) leaflets, the terminal leaflet
small or often absent; leaflets lanceolate to ovate-lanceolate, (3–)6–15 cm long, 1.5–5.5 cm wide, pointed at the tip,
rounded and uneven at the base, the margins conspicuously toothed, the upper surface yellow-green and glabrous except
for scattered capitate-glandular and other hairs on the midrib, the lower surface paler, with capitate-glandular
hairs, and other hairs and scales; foliage aromatic with distinctive spicy odor, turning yellow in fall.
Buds: terminal buds blunt, broadest at the base and slightly rounded at the top, slightly flattened, pale brown, hairy, 8–10
mm long; lateral buds smaller.
Flowers: unisexual, inconspicuous, male and female flowers on the same tree (plants monoecious), appearing with the
leaves; male flowers in hanging, 5–10 cm long, yellow-green catkins; stamens 17–50 per flower; female flowers usually
1–4 per short spike at the end of new growth, each with a single pistil.
Fruits: large, globose, single or in pairs, 3.5–8 cm in diameter, the outer husk thick, green to yellow-green, turning dark
brown at maturity (capable of staining skin or clothing), slightly hairy, not splitting open to expose nut, with distinctive
spicy odor; nut globose, 3–4 cm diameter, its shell (visible only when the outer husk of fruit is removed) irregularly
and deeply furrowed, the surface between grooves coarsely warty, the kernel 4-lobed, oily, sweet.
Bark: medium to dark gray or brownish, to almost blackish, darkening with age, deeply split into narrow, rough, intersecting
ridges.
Wood: sapwood whitish to yellowish brown (in the trade commonly darkened by streaming or staining to match the
heartwood); heartwood light brown to rich chocolate or purplish brown (the lighter shades from trees grown in the
open); wood with mild characteristic odor; grain straight or irregular (the wavy, curly figures for which this wood is
famous come from burls, crotches, and stump wood); growth rings distinct.
Habitat: stream bottom woods or rich woods on calcium rich soils, with best growth on deep, well-drained, fertile soils.
Range: Pineywoods and northern Gulf Prairies and Marshes west to East Cross Timbers and eastern Edwards Plateau, plus
several locations in northwest Texas; widespread in the eastern and central U.S. w to SD and TX.
Principal Uses: this is one of the most valuable North American woods and is considered by some to be the finest cabinet
wood; currently, because of its rareness, more BLACK WALNUT is being made into veneer, with the veneer used extensively
in furniture and cabinets; the lumber is used for gunstocks (absorbs recoil and does not shrink or warp with age),
furniture, paneling, caskets, and coffins; the ground shells are variously used, including as a non-slip agent for automobile
tires and as a filtering agent for scrubbers in smoke stacks.
Historical Uses: furniture, gunstocks, radio, television, and phonograph cabinets, piano cases, sewing machines,
woodenware, and in pioneer times (when it was abundant) railroad ties and rail fences; Native Americans and settlers
obtained a brown dye from the husk of the fruit.
Other Significant Information: although Juglans nigra is not an abundant tree in East Texas, it is certainly commercially
important. The wood, which is richly colored, beautifully grained, and easily worked, is so valuable that a single tree
can be worth thousands of dollars, and trees are sometimes “rustled.” This species exhibits allelopathy, the inhibition of
one plant by another via the release of chemicals into the environment. The chemical secreted is known as juglone, and
it has been investigated for pharmaceutical and other applications. There are at least 73 patents involving juglone,
demonstrating a range of potential applications from a drug useful for AIDS treatment to hair-dyes. Juglone is secreted
primarily by roots but is also found in other tissues (e.g., leaves) and can continue to be secreted for several years after a
tree has been cut. The chemical, technically a naphthoquinone, inhibits the growth of many plants, especially vegetables,
though some species are tolerant. Because of the possible allelopathic effects, some organic gardeners are careful
concerning the use of BLACK WALNUT leaves as mulch. Horses have developed laminitis, a malady of the hoof, from bedding
in stalls filled with small portions of walnut shavings. The nuts have a strong distinctive taste and are used in
baked goods and ice cream. The walnut species now used most frequently commercially is the Old World J. regia L.,
ENGLISH or PERSIAN WALNUT.
Recognition in the Field: alternate, pinnately compound leaves with (9–)15–19(–23) leaflets, the terminal 2–3 leaflets
usually smaller than the middle lateral leaflets; fruits large, round, nut-like, with an indehiscent husk.