Black Walnut

Illustration of black walnut compound leaf and nuts.
Edible
Scientific Name
Juglans nigra
Family
Juglandaceae (walnuts)
Description

Black walnut is a large tree with a straight trunk and rounded, open crown. The nuts, spicy odor, large feather-compound leaves, and chambered pith in the twigs help identify it.

Leaves are alternate, compound, 1–2 feet long, with 11–23 leaflets. Leaflets 3–5 inches long, 1–2 inches wide, broadest below the middle, the end leaflet smaller than side ones or absent; margin toothed; upper surface yellow-green; lower surface paler, hairy.

Bark is grayish-brown or black, grooves deep, ridges broad with sharp or rounded edges, roughly forming diamond-shaped patterns, chocolate-colored when cut.

Twigs are stout, rigid, brown to gray-brown, hairy; end bud about ½ inch long; pith light brown, chambered when cut lengthwise.

Flowers April–May. Male flowers in catkins, female flowers in a short spike on the same tree.

Fruits September–October, usually single or in pairs. A green, rounded husk, 1½–2½ inches across, covers the round, hard, bony, dark brown or black nut. The kernel is oily, sweet, and edible.

Similar species: Butternut, or white walnut (Juglans cinerea), is scattered and declining in the eastern two-thirds of Missouri, mostly in low and moist soils. It has rather cylindrical fruits, and the nut inside has 4 lengthwise ribs; leaf scars have the upper edge straight (not notched), bordered by a well-defined velvety ridge. The mild-tasting English (or Persian) walnut is the species J. regia. It is native to Eurasia and when cultivated in Missouri does not escape. The state of California grows nearly all of the US commercial supply of English walnuts. Walnuts are in the same family as hickories and pecans.

Size

Height: to 90 feet.

Where To Find
image of Black Walnut Distribution Map

Statewide.

Black walnut grows throughout Missouri in a variety of soils. It grows best on the deep, well-drained soils of north Missouri and on alluvial (river-deposited) soils in the south. Every farm in the state should grow some walnut trees. In addition to providing valuable wood, the walnut’s nutmeats are a major industry in the state. Even the hard shells can be used as an abrasive and to make activated carbon. It is Missouri’s most valuable tree.

Black walnut has been designated as Missouri's official state tree nut. Most of the state’s large, old walnut trees were felled in previous decades for lumber and other uses, yet the superb wood from this species remains in high demand. Young landowners have been planting walnuts in hopes of harvesting them in future decades. Several serious pests may endanger the health of Missouri's walnuts; educate yourself about thousand cankers disease (TCD), ambrosia beetles, walnut anthracnose, and other diseases, and never, ever transport firewood.

Missouri is the world’s top producer of black walnuts, which are used in baking and confections and even pickled whole. It would probably be eaten by more people if getting the nutmeats out of the nut were easier.

Walnut is the finest wood in the world. In the past, the warm brown hardwood was used lavishly in homes, barns, and fences. Today it’s used for furniture, veneer, and gunstocks.

There are records of old-time Ozarkers scattering the fresh leaves of black walnut, or of its close relative, butternut, about the house to repel insects such as bedbugs and fleas.

The nuts are eaten by mice and squirrels.

The leaves are eaten by larvae of luna moths, regal moths, and others. The presence of such caterpillars naturally attracts warblers and other insectivorous birds.

Walnut trees produce a chemical, juglone, that stunts or kills other plants growing nearby.

Media Gallery
Illustration of black walnut compound leaf and nuts.
Black walnut, Juglans nigra.
Paul Nelson
1/15
Photo of a black walnut tree.
Black walnut trees grow up to 90 feet tall with a rounded, open crown.
Chris Starbuck, University of Missouri
2/15
Image of a black walnut leaf
MDC Staff
3/15
Photo of black walnut leaves.
Black walnut leaves have 13 to 23 leaflets on green stalks. The leaflets are pointed with toothed edges and have a strong aroma when crushed.
Paul Wray, Iowa State University
4/15
A fragment of a black walnut shell after a squirrel had chewed it open
It is truly amazing how squirrels can open up the hard, bony nuts of black walnuts using only their teeth.
5/15
Photo of black walnut catkins.
Male flowers appear in drooping catkins when leaves emerge in spring.
Paul Wray, Iowa State University
6/15
Photo of still-small black walnut fruit developing on the tree, with a quarter next to it for scale
The female black walnut flowers mature to become the fruit. This image shows development as of May 21 in 2009.
7/15
unripe-black-walnuts
8/15
ripe-black-walnuts
9/15
Walnut scraps on a rock, left by a squirrel
Missouri hikers often see the remains of black walnut hulls and nuts lying on rocks or logs in the woods: this is where a squirrel had dinner!
10/15
Photo of black walnut bark and a pocket knife, showing brown color of scraped bark.
Black walnut bark is rough, and when the surface is lightly scraped it shows a chocolate brown color.
Simeon Wright
11/15
Photo of a black walnut twig cut down the middle, showing central pith.
Black walnut twigs are thick, light brown, with fuzzy buds and tan, chambered pith at the core of the twig.
Paul Wray, Iowa State University
12/15
Photo shows declining black walnut tree
Black walnut trees in Missouri can display die-back for many other reasons besides TCD.
Simeon Wright
13/15
Photo of a vial of walnut twig beetles.
More than 23,000 walnut twig beetles emerged from two firewood-sized pieces of black walnut wood.
Whitney Cranshaw, Colorado State University
14/15
Black Walnuts
David Stonner
15/15
Illustration of black walnut compound leaf and nuts.
Free to use
Photo of a black walnut tree.
Image of a black walnut leaf
Free to use
Photo of black walnut leaves.
A fragment of a black walnut shell after a squirrel had chewed it open
Free to use
Photo of black walnut catkins.
Photo of still-small black walnut fruit developing on the tree, with a quarter next to it for scale
Free to use
unripe-black-walnuts
ripe-black-walnuts
Walnut scraps on a rock, left by a squirrel
Free to use
Photo of black walnut bark and a pocket knife, showing brown color of scraped bark.
Photo of a black walnut twig cut down the middle, showing central pith.
Photo shows declining black walnut tree
Photo of a vial of walnut twig beetles.
Black Walnuts
Free to use
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About Trees, Shrubs and Woody Vines in Missouri
There are no sharp dividing lines between trees, shrubs, and woody vines, or even between woody and nonwoody plants. “Wood” is a type of tissue made of cellulose and lignin that many plants develop as they mature — whether they are “woody” or not. Trees are woody plants over 13 feet tall with a single trunk. Shrubs are less than 13 feet tall, with multiple stems. Vines require support or else sprawl over the ground.