11 Species of Walnut Trees for North American Landscapes

Black walnut tree

 

seven75 / Getty Images

The botanical name for the walnut tree genus is Juglans, which translates to "Jupiter's nut." It belongs to the Juglandaceae family, a group that also includes hickories and pecans (Carya spp.). Technically, the walnut fruit is not a nut, but rather a drupe—a stone fruit in which an outer fleshy skin surrounds a hardened shell protecting a seed inside.

Walnut trees are monoecious, meaning a single tree contains both male (catkin) and female (pistillate) flowers, allowing the trees to self-pollinate. Nut production is best when walnut trees of different cultivars are planted in groups, as is typically done in walnut groves cultivated for nut production.

When choosing a walnut tree for planting on your property, look closely at the recommended U.S. Department of Agriculture hardiness zones, as well as the tree height and sun exposure recommendations.

Warning

Walnuts are toxic to many plants. It is important to choose the plants around your walnut trees carefully. This genus produces a toxin called juglone that can be harmful in varying degrees to the plants around it, through an effect known as allelopathy. The chemical juglone is a genetic adaptation that keeps vegetation from growing around the base of the walnut plant. Make sure any surrounding or companion plants you are considering are not prone to juglone toxicity.

  • 01 of 11

    Andean Walnut (Juglans neotropica)

    Nogal en Fragen
    horrabin/Flickr/CC BY 2.0

    The Andean walnut is a slow-growing tree tall It has grooved, red-brown bark and an oval-shaped canopy. It has large leaves (more than 1 foot long) that consist of pointed, serrated leaflets arranged in pairs. This tree is also known regionally as Columbian walnut, Ecuador walnut, Peruvian walnut. It is generally grown for nuts or for its highly prized wood, and it is an endangered species in its native range. It is rarely grown in the U.S.

    • Native Area: Colombia, Ecuador, and Peru
    • USDA Growing Zones: 10 to 11
    • Height: Up to 130 feet; more commonly, 50 to 65 feet
    • Sun Exposure: Full to partial sun; cannot grow in shade
  • 02 of 11

    Arizona Black Walnut (Juglans major)

    Juglans major (Arizona Walnut). Morton Arboretum acc. 614-47*1. 52 years old at this photo, grown from seed.
    Bruce Marlin/Wikimedia Commons/CC 3.0

    In moist conditions, the tree features a single, stout trunk. In drier conditions, there are usually several slender trunks. The leaves are 8 to 14 inches long and pinnately compound (grouped in leaflets around a central stem). Regionally, this tree is sometimes known as New Mexico walnut, mountain walnut, or river walnut. This tree prefers moist soil, and in the dry territory that is its native range, the tree seeks out ravines and river beds.

    • Native Area: Mexico and Southwest U.S. (Arizona, New Mexico, Oklahoma, Texas, Utah)
    • USDA Growing Zones: 6 to 10
    • Height: Up to 50 feet
    • Sun Exposure: Full sun to part shade
  • 03 of 11

    Black Walnut (Juglans nigra)

    Black walnut tree

     

    nickkurzenko / Getty Images

    The walnuts from this tree are cultivated for their distinctive and desirable taste. These trees are also grown for their hard, attractive wood. Many cultivars of this tree have been developed for improved quality nuts or wood. The black walnut has sharply ridged gray-black bark that forms diamond shapes, and the trunks may be quite long before reaching the first branches. The tree crowns are usually dense and rounded. The leaves are huge, up to 24 inches long consisting of 13 to 23 lance-shaped leaflets. Autumn color is a fairly bland yellow. This tree is sometimes known as the American walnut or the eastern black walnut.

    • Native Area: Eastern U.S.
    • USDA Growing Zones: 4 to 9
    • Height: 50 to 120 feet
    • Full Exposure: Full sun
  • 04 of 11

    Butternut (Juglans cenerea)

    Butternut tree

     

    Dan Mullen / Flickr / CC By 2.0

    The butternut is a deciduous tree growing up to 60 feet tall. It is a slow-growing species that rarely lives longer than 75 years. It is similar in appearance to the black walnut, but it is a smaller tree with less fissured bark, fewer leaflets per leaf, and smaller nuts that are more oval-shaped than round. Once a very common North American specimen, the butternut has become increasingly rare due to a spreading canker disease. In different regions, it may be known as oilnut, white walnut, or long walnut.

    • Native Area: Eastern North America
    • USDA Growing Zones: 3 to 7
    • Height: 40 to 60 feet
    • Sun Exposure: Full sun
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  • 05 of 11

    Brazilian Walnut (Juglans Australis)

    Walnut tree in a field
    George Slickers/Wikimedia Commons/Creative Commons 2.5

    J. australis is a spreading deciduous tree, up to 80 feet wide, which produces first quality lumber, with its trunk straight up. The immature and mature fruits of this tree are also consumed. The Brazilian walnut (also known as the nogal criolla, or tropical walnut) is a tropical tree that is rarely grown in North America, but is sometimes planted as an ornamental shade tree in tropical zones.

    • Native Area: Argentina and Bolivia
    • USDA Growing Zones: 10 to 11
    • Height: Up to 80 feet
    • Sun Exposure: Full sun
  • 06 of 11

    California Black Walnut (Juglans californica)

    California Black Walnut in Puente Hills.
    Animalparty/Wikimedia Commons/CC 2.5

    The California black walnut can be either a large shrub with one to five main stems, or a small, single-trunked tree. The main trunk often forks close to the ground, making it appear that two trees have grown together. The California black walnut has deeply channeled thick bark that furrows with maturity. It has the familiar walnut leaves—pinnately compound with 11 to 19 lance-shaped leaflets. The nuts are small, hard, and difficult to remove. This plant may also be called the southern California black walnut.

    • Native Area: Southern California
    • USDA Growing Zones: 8 to 10
    • Height: 15 to 40 feet
    • Sun Exposure: Full sun
  • 07 of 11

    English Walnut (Juglans regia)

    An english walnut tree in an open field
    Thesupermat/Wikimedia Commons/CC BY S.A. 3.0

    This tree is an Old World walnut tree that is called the English walnut, but it actually comes from China. This tree's history reaches back to stories involving Alexander the Great when he first introduced this tree as Persian in origin. This is the walnut that provides more of the edible walnuts sold in stores. Smooth olive-brown bark on young trees gradually turns silvery gray and rough as the tree ages. The compound leaves are 10 to 16 inches long, clustered in 5 to 9 lance-shaped leaflets. The fruits fall in autumn, and the nuts are relatively thin-shelled with richly flavorful seeds inside. This tree is also known as the common walnut or Persian walnut. Many named cultivars are available.

    • Native Area: Europe and Asia
    • USDA Growing Zones: 5 to 9
    • Height: 40 to 60 feet; occasionally to 120 feet
    • Sun Exposure: Full sun
  • 08 of 11

    Northern California Black Walnut (Juglans hindsii)

    California Black Walnut in Puente Hills.
    Animalparty/Wikimedia Commons/CC 2.5

    The north California walnut, also called Hind's black walnut, is a medium-sized tree with a short, bulky look, since the crown is often wider than the height of the tree. The trunk on mature trees can be 5 to 6 feet in diameter at the base. The leaves are about 1 foot long, with 13 to 21 leaflets with dentate (coarsely toothed) margins.

    Juglans hindsii has only one confirmed native stand remaining. It is considered seriously endangered in California, threatened by hybridization with orchard trees, urbanization, and habitat loss. Some authorities consider this plant a variation of the California walnut, giving it the name Juglans californica var. hindsii.

    • Native Area: California
    • USDA Growing Zones: 7 to 10
    • Height: 30 to 60 feet
    • Sun Exposure: Full sun
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  • 09 of 11

    Japanese Walnut (Juglans ailantifolia)

    Heartnut (Juglans ailantifolia) in flower
    Tahirs/Wikimedia Commons/CC 1.0

    This is a deciduous tree with light grey bark. The male flowers are yellow-green catkins produced in spring when new foliage appears. The female flowers have attractive pink or reddish pistils. The large leaves (up to 24 inches) are pinnately compound, with 11 to 17 leaflets that are a lighter green in color than most trees. Other common names for this tree include heartnut and siebold walnut.

    • Native Area: Japan
    • USDA Growing Zones: 4 to 7
    • Height: Usually 40 to 65 feet; occasionally to 100 feet
    • Sun Exposure: Full sun
  • 10 of 11

    Manchurian Walnut (Juglans mandshurica)

    Manchurian Walnut on a tree branch
    Jean-Pol GRANDMONT/Wikimedia Commons/CC BY 2.5

    The tree is exceptionally hardy (down to at least minus 45 degrees F.). It has a relatively short vegetation period compared to other walnuts, grows rapidly, and is cultivated as an ornamental in colder temperate regions all over the Northern Hemisphere. Its nuts are edible but small and difficult to extract. Its compound leaves have 7 to 19 leaflets, each 2 1/2 to 6 1/2 inches long. The fissured bark is grayish-brown in color. This can grow to be a fairly massive tree, with a trunk up to 6 1/2 feet in diameter. The tree grows quite fast, achieving its adult size within 20 years.

    Manchurian walnut makes a good ornamental yard tree in colder parts of North America, especially since contains less of the toxic juglone chemical than other popular walnuts. It is sometimes known as the Chinese walnut.

    • Native Area: China, North and South Korea, Russian Far East
    • USDA Growing Zones: 2 to 8
    • Height: Up 60 feet; occasionally to 100 feet
    • Sun Exposure: Full sun
  • 11 of 11

    Little Walnut (Juglans microcarpa)

    Texas black walnut
    Jerry Friedman/Wikimedia Commons/CC BY 2.0

    The little walnut is a large shrub or small tree that grows wild along streams and ravines. Its name derives from nuts that are only about 1/2 to 3/4 inch wide, but because it commonly grows around stream beds and ravines in Southwestern regions, you may also hear it called Texas walnut, Texas black walnut, or Mexican walnut. This plant usually branches out near the ground and has a broad rounded crown. The bark is gray to dark brown and develops deep fissures over time. The pinnately compound leaves have narrow leaflets 2 to 2 1/2 inches long, with finely serrated edges.

    • Native Area: Kansas, New Mexico, Oklahoma, Texas
    • USDA Growing Zones: 7 to 9
    • Height: 15 to 50 feet
    • Sun Exposure: Full sun to part shade

Growing Tip

Like most landscape trees, walnuts will grow best if they receive full sun. However, walnuts have less tolerance for dry conditions than many trees; they need moist but well-drained soil, and they often struggle in regions that receive less than 25 inches of rain each year. If you live in a dryer area, you'll need to be very diligent about irrigating your walnut tree.