Walnut Trees: Types, Bark and Leaves – Identification Guide (Pictures)

Walnut trees are large deciduous trees with rounded canopy of green, lush foliage. Most walnut trees have dark, ridged bark, pinnate feather-like leaves, and globular drupes that contain a nut. Walnut trees grow to between 33 and 131 ft. (10 – 40 m) tall with a massive spread up to 50 ft. (15 m). Walnut trees are in the plant genus Juglans and they are famous for their delicious nuts and beautiful wood.

This guide to walnut trees helps you identify the different types of species in the genus. You’ll find descriptions of varieties of walnut tree leaves, nuts, and their bark.

Walnut Tree Facts

There are 21 species of walnut trees in the walnut family Juglandaceae. The most common walnut tree varieties are black walnut, and English walnut trees. Other walnut tree varieties are butternut, California black walnut, Andean walnut, Japanese walnut, and little walnut.

Varieties of walnut trees are native to Europe, North America, Asia, and China.

Most people associate walnut trees with the delicious nuts they produce. Botanically speaking, the walnut tree’s fruit is actually not a nut but a drupe. The nut is actually the seed of the walnut tree’s fruit. The walnut’s fruit has outer fleshy green husk surrounding a hard shell that contains the seed (which we call walnut). A whole walnut resembles the appearance of a brain.

Walnut timber is a prized type of hardwood for making furniture. The wood of walnut trees is a dark brown, almost chocolatey color. The texture, beautiful grain, and walnut wood color make it ideal for carving bowls, making cabinets, or using it as a veneer.

Walnut Tree Varieties

The three most common walnut tree varieties are:

• Black walnut (Juglans nigra). Black walnut tree has dark-colored bark with deep furrows giving the tree trunk a rough feel. The nuts on black walnuts grow in a rounded green husk, and the tree’s foliage is made up of pinnate leaves.
• Butternut (Juglans cinerea) or white walnut trees. Butternut trees have a light gray bark with a smoother feel than black walnuts. As with all species of walnut, butternut tree leaves are pinnate with up to 17 leaflets. The drupes are an oval, rather than a rounded shape.
• English walnut (Juglans regia) trees. English walnut trees have olive-brown, smooth bark when young that gradually develops wide fissures. Like all species of walnut, leaves are pinnate, but English walnut leaves are smaller. The whole fruit of English walnut trees is edible with a rich flavor.

Walnut Tree Bark

The bark of walnut trees is generally rough with deep fissures. The ridges run vertically up and down the trunk. Depending on the species, walnut bark can be light gray to dark brown. Removing the bark from English walnut or black walnut trees reveals a dark brown wood.

The bark helps differentiate between the species of walnut trees. Butternut (white walnut) bark is whitish-gray and smooth to the touch. English walnut and black walnut bark have deep vertical crevices and are a darker color.

Walnut Tree Leaves

All 21 species of walnut trees have feather-like pinnate leaves. There are usually two to nine pairs of leaflets on each blade and one more leaf at the tip. Leaves turn yellow or brown in the fall. Crushing walnut leaves reveals a distinct spicy citrus aroma.

Comparing the three common walnut tree species, butternut (white walnut) tree has oblong-lanceolate leaves. In contrast, English and black walnut trees have shorter, more rounded leaflets.

The difference between black walnut and other species is that its leaves have a small terminal leaflet that sometimes is missing. However, butternut and English walnut trees always have a large leaflet at the tip.

Walnut Tree Nuts

Walnut trees can be identified by their distinct nuts (or drupes). The fruits that grow on walnut trees look like small green balls. The outer green layer surrounds the nutshell and kernel or nut. The nuts of walnut trees have two halves that have a bumpy texture with a papery covering.

Walnut Tree Identification

The best way to identify species of walnut trees is by their bark, leaves, and nuts. Their bark is light gray to dark brown. Walnut leaves are pinnate, but some species have larger leaves than others. Walnut nuts look similar, but the taste and texture between the species can differ.

Walnut tree bark usually has deep ridges running vertically up and down the trunk. The walnut bark color can be brown to dark gray and have diamond-shaped patterns. Some varieties of walnut trees have smoother, lighter bark.

Walnut tree leaves are pinnate that have pairs of leaflets. Most walnut leaves also have a single leaf at the end of the twig. The largest leaflets are at the center, and the leaves have between 5 and 25 leaflets. All walnut tree foliage turns brown or yellow in the fall.

Walnut tree nuts growing on the tree look like small round or oval green balls. The walnut nut or seed is contained in a hard-brown shell. The taste of walnuts ranges from earthy to mild and sweet.

Types of Walnut Trees (With Pictures)

The most common walnut trees are the black walnut, English walnut, and butternut or white walnut. However, other varieties of walnut are found in South America, Asia, and southeastern Europe. It’s the black walnut and English walnut that are famous for their timber. English walnut nuts are the sweetest.

Here is information about the identifying features of the most popular types of walnut trees.

Black Walnut (Juglans nigra)

The black walnut tree has dark, deeply fissured bark and grows to between 75 and 130 ft. (22 – 40 m) tall. The deciduous walnut tree is native throughout North America’s eastern part in USDA zones 4 – 9. Black walnut trees have medium growth, and they prefer to grow in sunny areas.

Black walnuts are also called the eastern American black walnut or American walnut. Their native habitat is from southern Ontario to northern Florida and they grow in forests and woodlands. These walnut trees can live up to 130 years.

The black walnut tree has a large, rounded crown of large pinnate leaves. The spread of the sizeable nut-bearing tree can be as wide as it is tall.

Black walnut tree leaves and stems have a pungent citrus-like odor.

The male and female species of black walnut trees produce flowers. The male walnuts have long catkins that hang from the branches. The female walnut produces small clusters of flowers on the end of short spikes.

After flowering, the black walnut tree produces globe-shaped green fruits that look like green balls – they are are 2” (5 cm) in diameter.

When the black walnuts have just fallen from the tree they look like rough green balls. As they mature on the ground, their husk turn from green to very dark brown (or even black). Inside the tough husk is the hard shell protecting the edible nut.

Another distinguishing feature of black walnut trees is that they produce toxic chemicals in the soil. You can tell black walnut trees because plants don’t grow in a 50 to 80 foot (15 – 24 m) radius around the tree.

Walnut tree bark: The black walnut tree has dark gray to brown bark with deep ridges in diamond shapes. The distinctive bark pattern makes it easy to identify black walnut trees in the winter.

Walnut tree leaves: Black walnut leaves are pinnately compound with 15 to 23 leaflets on each twig. Leaflets are 3” to 4” (7 – 10 cm) long. The leaves have a slightly serrated edge and are an ovate, lanceolate shape. Leaves turn yellow in the fall.

Butternut or White Walnut (Juglans cinerea)

Butternut or white walnut trees have smooth gray bark, grow up to 66 ft. (20 m), and produce delicious nuts. Butternut trees resemble black walnut trees, only that they are smaller with smoother bark. White walnuts grow in full sun and thrive in zones 3 to 7.

Butternut trees has a few distinguishing features to tell them apart from other walnut species. For example, the fruit of butternut trees are oval, not round. Their leaves tend to have fewer leaflets. White walnut trees don’t tolerate the heat as much as black walnut trees.

Compared to black walnuts, butternut walnuts have a buttery taste, not earthy like the black ones.

White walnut trees also emit toxic chemicals in the ground. However, this is not as strong as black walnut and doesn’t affect surrounding plants as much.

Walnut tree bark: Butternut tree bark is gray and smooth when the tree is young and only becomes rough and fissured when the walnut tree is mature.

Walnut tree leaves: Butternut tree leaves contain between 11 and 23 leaflets which have an oblong, lanceolate shape up to 5” (12 cm) long. The leaflets have toothed-edges, and they come to a distinct tip. The leaf stems always have a single large tip or terminal leaf.

English Walnut (Juglans regia)

The English walnut tree has smooth olive-colored bark when young that becomes deeply fissured and gray as it matures. English walnuts grow to around 65 ft. (20 m) with a crown of pinnate leaves just as wide. English walnut trees are the primary source of walnuts sold in stores today.

The English walnut tree is also called the Persian walnut, Madeira walnut, and Carpathian walnut. These common names for the walnut tree relate to the tree’s native habitat in southern Europe. Common walnut trees thrive in full sun and grow in zones 5 – 9.

Like black walnut trees, English walnuts produce round drupes and tasty nuts.

English walnuts (Juglans regia) look like green tennis balls when they are on the tree. But after falling to the ground, their rough green husks turn from green color to a very dark brown (almost black) color.

The taste of English walnuts is described as mild and pleasant. You can also eat the whole nut, and pickled walnuts are a delicacy in some parts of Europe.

Walnut tree bark: English walnut trees have deep gray to brown bark with deep, rounded fissures.

Walnut tree leaves: English walnut tree’s pinnate leaves contain between 5 and 9 leaflets, and they always have a single blade at the tip. Individual leaflets are 4” to 7” (10 – 18 cm) long. Compared to butternut and black walnuts, there are fewer leaflets on English walnut trees.

California Black Walnut (Juglans californica)

The California black walnut tree is an uncommon large, multi-stemmed shrub or small tree with a single trunk. California walnuts grow to between 20 and 50 ft. (6 – 15 m) tall and thrive in warm climates and full sun. These small walnut trees grow in zones 7 – 10.

Walnut tree bark: California black walnut trees have thick bark that is a dark gray color. The bark is recognizable with its deep furrows running up and down the trunk.

Walnut tree leaves: California black walnut tree leaves are smooth with slight serration along the margins. Between 11 and 19 elongated leaflets make up the pinnate leaves.

Northern California Black Walnut (Juglans hindsii)

The Northern California walnut tree has a single trunk, and the tree grows up to 60 ft. (18 m) tall. Also called Hinds’ black walnut or claro walnut, the tree is mostly used in the lumber industry. These black walnut trees grow in dry, sunny climates in zones 8 and 9.

Walnut tree bark: Northern California black walnuts have dark gray bark with moderate fissuring on the trunk.

Walnut tree leaves: The ‘Hinds’ black walnut’s leaves are about 12” (30 cm) long. The blades are made up of 13 – 21 leaflets up to 5″ (12 cm) long. There are some small tufts of hair on the leaves.

Arizona Black Walnut (Juglans major)

Arizona black walnut is a small walnut tree that grows up to 50 ft. (15 m) tall. The short trunk supports a vast, broad, spreading crown that’s up to 65 ft. (20 m) wide. Arizona walnut trees produce small edible nuts.

Walnut tree bark: Arizona black walnuts have gray-brown bark with deep furrows and flat-topped ridges.

Walnut tree leaves: Like all species of walnuts, Arizona walnut trees have pinnately compound leaves. Each leaf contains between 9 and 15 leaflets that are pointed and oblong.

Andean Walnut (Juglans neotropica)

Andean walnut trees are slow-growing trees in the genus Juglans. Andean walnuts grow up to 131 ft. (40 m) tall and are found in the mountains of Peru, Columbia, and Ecuador. These tropical walnut trees are prized for their high-quality red-colored timber. Other names for this walnut species are Columbian walnut, Ecuadorian walnut, and Cedro negro.

Walnut tree bark: The Andean walnut tree has reddish-brown bark that has deep, long grooves.

Walnut tree leaves: The tropical walnut has long leaves up to 15” (40 cm). The walnut leaves comprise of pointed oval leaflets.

Japanese Walnut (Juglans ailantifolia)

Japanese walnut trees are similar to butternut trees due to their leaf shape and buttery nuts. These Asian walnut trees grow up to 66 ft. (20 m) and have light gray bark. An unusual feature of these walnuts is that the fruits are heart-shaped rather than round or oval.

Walnut tree bark: Japanese walnuts have light gray bark with grooves that form a network pattern.

Walnut tree leaves: Japanese walnut trees have leaves that are 2 ft. (60 cm) large, containing between 11 and 17 large leaflets. Each leaflet can be up to 6” (16 cm) long.

Little Walnut (Juglans microcarpa)

Also called the Texas black walnut, this small walnut species is a large tree-like shrub. The Texas walnut tree grows to between 10 and 30 ft. (3 – 9 m) tall. The sun-loving walnut shrub grows in zones 7 – 9. However, its timber and fruit are insignificant and are of little use.

Walnut tree bark: The little walnut tree has gray to dark brown bark with deep furrows in indistinct patterns.

Walnut tree leaves: The little Texas walnut tree’s leaves have between 7 and 25 small leaflets with smooth or slightly serrated margins.

Manchurian Walnut (Juglans mandshurica)

The Manchurian walnut tree is native to East Asia and is one of the cold hardiest walnut trees. The fast-growing tall walnut trees are sometimes grown as ornamental trees because their nuts are small and difficult to extract. Manchurian walnuts are cold hardy in zones 2 – 8 and can withstand temperatures as low as -49°F (-45°C).

Walnut tree bark: The Manchurian walnut tree has grayish-brown bark with fissuring common to most walnut tree species.

Walnut tree leaves: The pinnately compound leaves of the Manchurian walnut tree have 3 to 9 pairs of leaflets with a single terminal leaf.

Related articles:

• Elm Trees: Identification, Bark and Leaves
• Types of Oak Trees with Their Bark and Leaves
• Types of Willow Trees: Weeping, Shrubs, Dwarf and More