Black Walnut

Juglans nigra

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Illustration of black walnut compound leaf and nuts.
Black walnut, Juglans nigra.
Paul Nelson
Edible
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.

Key Identifiers

 

  • Leaves long, alternate, feather-compound
  • Leaflets 11–23, toothed
  • Fruits distinctive
  • Bark grayish, deeply grooved with rather diamond-shaped patterns, ridges broad
  • Twigs stout, with chambered pith
  • Distinctive spicy odor
Size

Height: to 90 feet.

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Photo of a black walnut tree.
Black Walnut Tree
Black walnut trees grow up to 90 feet tall with a rounded, open crown.

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Image of a black walnut leaf
Black Walnut

black-walnut-leaves01-18-2011.jpg

Photo of black walnut leaves.
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.

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Black Walnuts
Black Walnuts

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Photo of black walnut catkins.
Black Walnut Catkins
Male flowers appear in drooping catkins when leaves emerge in spring.

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Photo of black walnut bark and a pocket knife, showing brown color of scraped bark.
Black Walnut Bark
Black walnut bark is rough, and when the surface is lightly scraped it shows a chocolate brown color.

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Photo of a black walnut twig cut down the middle, showing central pith.
Black Walnut Twig Cross Section
Black walnut twigs are thick, light brown, with fuzzy buds and tan, chambered pith at the core of the twig.

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unripe-black-walnuts
Unripe Black Walnuts

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Photo shows declining black walnut tree
Declining Black Walnut Tree
Black walnut trees in Missouri can display die-back for many other reasons besides TCD.

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Photo of a vial of walnut twig beetles.
Don't Accidentally Spread TCD
More than 23,000 walnut twig beetles emerged from two firewood-sized pieces of black walnut wood.

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Black Walnuts
Black Walnuts
Habitat and conservation

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.

image of Black Walnut Distribution Map
Distribution in Missouri

Statewide.

Status

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.

Human connections

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.

Ecosystem connections

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.