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. With a little practice, you can identify this common tree from a distance by the distinctive pattern of its branches.
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.
- 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
- 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.
Height: to 90 feet.
Habitat and Conservation
Scattered to common, growing in bottomland forests, rich/moist upland forests, bases of bluffs, and banks of streams and rivers. Also grows along margins of pastures and crop fields, railroads, and roadsides. Frequently grows in people's yards. It can live 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.
Native deciduous hardwood tree. Especially valuable for its lumber and for its edible nuts.
Black walnut has been designated as Missouri's official state tree nut. 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 Missouri. Even the hard shells can be used as an abrasive and to make activated carbon. It is Missouri’s most valuable tree.
Missouri is the world’s top producer of black walnuts, which are used in baking, confections, salads, ice cream, and even pickled whole. The nuts would probably be even more popular if getting the nutmeats out of the nut were easier. The nuts are high in protein and other nutrients. Many Missourians' family holiday recipes from immigrant grandmothers incorporated black walnuts as a frugal alternative to Old World nuts that were more expensive in America.
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. 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.
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.
Walnut is one of our early fall color trees, one of a host of native trees that turn yellow along streambanks in September. Compared to most other trees, the leaflets drop off early, leaving the walnut branches bare except for the big ripe walnuts. Frequently, in early fall, poison ivy can be seen clothing the walnut trunks and major branches, and the ivy's bright red leaves provide a colorful contrast to the golden yellow walnut leaves and green fruits.
In the past, dyes were extracted from the bark and green fruits.
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.
Black walnut nuts are often referred to as "hard mast." Acorns and other tough tree nuts also fall into this category, which is extremely important for many animals' winter survival. Black walnuts are eaten by mice and squirrels. These rodents commonly store the nuts in caches, then fail to eat them all. In this way, they distribute the nuts away from the parent plant and facilitate its spread. Tree squirrels' habit of storing nuts in the ground results in the eventual germination of many unrecovered nuts. Thus they essentially "plant" nuts that grow into trees that furnish not only food and shelter for subsequent squirrel populations, but also help renew woodlands with young sapling trees.
More than 20 species of moths have been documented feeding on black walnut, including the larvae of beautiful green luna moths, several species of underwing moths (Catocala spp.), the walnut sphinx, some dagger moths, some prominent moths (Datana spp.), and others. The impressive, spiky, hot-dog-sized caterpillars of the regal or royal walnut moth, called "hickory horned devils," feed on walnut leaves. Fall webworms (Hyphantria cunea) build their cobwebby "tents" around walnut branch tips late in the season.
Many other insects eat walnut leaves, flowers, nuts, wood, or sap, including a number of leaf beetles, longhorned beetles, lace bugs, stink bugs, plant bugs, aphids, and more. The black walnut curculio, a weevil, develops as a grub in the nuts and can cause early fruit drop (and disappointed human harvesters).
All this insect munching usually does not hurt a healthy walnut tree, and the presence of such caterpillars and other insects naturally attracts, and feeds, warblers and other insectivorous birds.
Like other large trees, walnuts provide important habitat for animals that live and hunt in trees. Together with other plants in the community, they shape and define their habitat: stream edge communities and bottomland forests, for instance, wouldn't be the same without them.
Walnut trees can reach large sizes and as they age, their hollow trunks and branches can house carpenter ants, snakes, bee colonies, squirrels, raccoons, opossums, owls, woodpeckers, chimney swifts, bluebirds, chickadees, and other cavity-nesting animals.
Walnut trees produce a chemical, juglone, that stunts or kills other plants growing nearby.