Black Walnut, Eastern Black Walnut, American Black Walnut
Juglans nigra, commonly known as Black Walnut, is a large, deciduous hardwood tree native to central and eastern North America. It is prized for its dark, richly grained wood and edible nuts. Beyond its economic value, it plays a significant role in ecosystems, supporting wildlife and acting as a pioneer species in forest succession, much like red maple (Acer rubrum), silver maple (Acer saccharinum), and black cherry (Prunus serotina).
Black Walnut is a member of the walnut family (Juglandaceae), which includes commercially important nut-producing trees such as pecan (Carya illinoinensis), Shagbark Hickory (Carya ovata), and Persian Walnut (Juglans regia).
Black Walnut thrives in riparian zones, extending from southern Ontario and central Michigan to Texas and Florida. It prefers deep, fertile, well-drained soils but can adapt to various conditions.
Black Walnut is a fast-growing, large deciduous tree with an open, rounded crown when grown in open spaces. In forests, it develops a tall, straight trunk due to competition for light.
Mature Black Walnut trees typically reach heights of 50-75 feet (15-23 m) with a spread of 50-75 feet (15-23 m). In optimal conditions, some specimens exceed 100 feet (30 m). Black Walnut grows 2-3 feet (0.6-0.9 m) per year when young, slowing to 1-2 feet (0.3-0.6 m) annually with age. It reaches 50-75 feet (15-23 m) in 30-40 years, depending on soil, moisture, and competition.
The tree can live for over 130 years, with some individuals surpassing 200 years in undisturbed forests.
Black Walnut is monoecious, producing male and female flowers on the same tree. Male flowers appear in long, drooping catkins (3-5 inches long), while female flowers are small, clustered spikes located at the branch tips. Pollination occurs via wind, and flowers emerge in mid to late spring.
The female flowers develop into large, round, sweet, edible nuts enclosed in thick, green husks. The nut’s hard, corrugated shell protects a rich, flavorful kernel, prized for its strong, distinctive taste. The nuts ripen in autumn, falling to the ground, where the husks gradually blacken and decompose as they rot away. If grown for nut production, it usually takes 30 years before a tree will produce a large crop of nuts. Black Walnut nuts are used in pies, cakes, cookies, and ice cream.
The leaves are large, pinnately compound, and can grow 1-2 feet (30-60 cm) long, consisting of 15-23 leaflets. Emerging late in spring, the dark green foliage turns bright yellow in autumn. When crushed, the leaves emit a strong, spicy odor.
The bark is dark brown to black, deeply furrowed, and forms a diamond-shaped ridge pattern. The inner bark has a distinct chocolate-brown color.
Black Walnut thrives in USDA zones 4-9, tolerating a range of temperatures. Within its optimal range, the average annual temperature is around 13°C (55°F), the frost-free season lasts at least 170 days, and the average annual precipitation is a minimum of 35 inches (89 cm). Black Walnut is drought, heat, drought, and compacted soil tolerant.
Recipient of the prestigious Award of Garden Merit of the Royal Horticultural Society.
Black Walnut plays a crucial role in supporting wildlife. Its nuts provide an important food source for many animals, including squirrels, deer, and various bird species. Eastern fox squirrels, in particular, rely on the nuts, which make up approximately 10% of their diet. Other rodents also consume the nuts, helping with seed dispersal.
The tree serves as a host plant for several insect species. It supports the larvae of the Hickory Horned Devil (Citheronia regalis). Black Walnut is also a larval host for the Banded Hairstreak Butterfly (Satyrium calanus) and the Luna Moth (Actias luna), both of which depend on the tree for their life cycle.
Beyond providing food, Black Walnut contributes to habitat diversity, offering shelter and nesting sites for birds and small mammals. Its dense canopy provides shade and cover, while fallen nuts sustain wildlife throughout autumn and winter.
Although not considered a choice browse, black walnut leaves are palatable to deer. The tree is generally resistant to rabbit damage.
Black Walnut (Juglans nigra) is allelopathic, producing a substance known as juglone that inhibits the growth of many plants. This chemical is released from the tree’s roots, leaves, and nut husks, creating unfavorable conditions for certain species. Plants highly sensitive to juglone include azaleas, rhododendrons, blueberries, peonies, and solanaceous crops such as tomatoes, peppers, and potatoes.
Beyond its effects on plant life, Black Walnut poses toxicity risks to animals and humans:
Poison Severity: Low to moderate, depending on exposure and species affected.
Though native, Black Walnut can aggressively colonize disturbed areas due to its rapid growth and ability to suppress competing vegetation through allelopathy.
Black walnut trees offer numerous benefits but also come with several challenges. Understanding both can help determine their suitability for specific landscapes and uses.
Black Walnut requires full sun for optimal growth and nut production. It is intolerant of shade.
Prefers deep, organically rich, well-drained, moist soils with a pH of 5.0–7.5, but can grow in a variety of soil types. This tree is difficult to transplant because of its deep taproot.
Water young trees regularly. Mature trees are drought-tolerant but perform best with consistent moisture.
Rarely necessary, but a balanced fertilizer can be applied in early spring. Avoid over-fertilizing, as it can reduce nut production.
Prune in the dormant season to maintain a strong central leader and remove dead or diseased branches.
Yes, it releases juglone, which inhibits the growth of many plants, including tomatoes, pines, and birches.
Nut production begins at 12-15 years, with peak production occurring around 30 years.
Yes, but they should be planted away from other plants sensitive to juglone.
Yes, it is one of the most valuable North American hardwoods used in fine furniture and veneer.
Yes, it provides food and shelter for numerous species, including squirrels, birds, and insects.
Yes, black walnuts are edible and highly nutritious. They have a rich, bold flavor that is stronger than English walnuts. However, they have thick, hard shells that require effort to crack, and the husks can stain hands and clothing.
Yes, black walnut is highly nutritious and rich in antioxidants, healthy fats, protein, and minerals. It is used in baking, confectionery, and traditional medicine. However, its strong flavor and tough shell make it more challenging to process than English walnuts.
No, black walnut trees are self-fertile, meaning a single tree can produce nuts. However, planting multiple trees improves pollination and increases nut yield.
Hardiness |
4 - 9 |
---|---|
Heat Zones |
5 - 9 |
Plant Type | Trees |
Plant Family | Juglandaceae |
Common names | Eastern Black Walnut, Black Walnut |
Exposure | Full Sun |
Season of Interest | Spring (Mid, Late), Summer (Early, Mid, Late), Fall |
Height | 50' - 75' (15.2m - 22.9m) |
Spread | 50' - 70' (15.2m - 21.3m) |
Maintenance | Average |
Water Needs | Average |
Soil Type | Chalk, Clay, Loam, Sand |
Soil pH | Acid, Alkaline, Neutral |
Soil Drainage | Moist but Well-Drained, Well-Drained |
Characteristics | Plant of Merit, Showy, Fruit & Berries |
Native Plants | United States, Northeast, Pennsylvania, Rhode Island, Connecticut, Delaware, Maine, Massachusetts, Maryland, New Hampshire, New Jersey, New York, Midwest, Minnesota, Missouri, Nebraska, Michigan, South Dakota, Kansas, Iowa, Indiana, North Dakota, Ohio, Wisconsin, Illinois, Southeast, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, West Virginia, Alabama, Arkansas, Florida, Georgia, Kentucky, Southwest, Texas, Oklahoma, Utah, Wyoming, Rocky Mountains |
Tolerance | Drought, Rabbit |
Attracts | Butterflies, Birds |
Garden Styles | Prairie and Meadow |
Hardiness |
4 - 9 |
---|---|
Heat Zones |
5 - 9 |
Plant Type | Trees |
Plant Family | Juglandaceae |
Common names | Eastern Black Walnut, Black Walnut |
Exposure | Full Sun |
Season of Interest | Spring (Mid, Late), Summer (Early, Mid, Late), Fall |
Height | 50' - 75' (15.2m - 22.9m) |
Spread | 50' - 70' (15.2m - 21.3m) |
Maintenance | Average |
Water Needs | Average |
Soil Type | Chalk, Clay, Loam, Sand |
Soil pH | Acid, Alkaline, Neutral |
Soil Drainage | Moist but Well-Drained, Well-Drained |
Characteristics | Plant of Merit, Showy, Fruit & Berries |
Native Plants | United States, Northeast, Pennsylvania, Rhode Island, Connecticut, Delaware, Maine, Massachusetts, Maryland, New Hampshire, New Jersey, New York, Midwest, Minnesota, Missouri, Nebraska, Michigan, South Dakota, Kansas, Iowa, Indiana, North Dakota, Ohio, Wisconsin, Illinois, Southeast, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, West Virginia, Alabama, Arkansas, Florida, Georgia, Kentucky, Southwest, Texas, Oklahoma, Utah, Wyoming, Rocky Mountains |
Tolerance | Drought, Rabbit |
Attracts | Butterflies, Birds |
Garden Styles | Prairie and Meadow |
How many Juglans nigra (Black Walnut) do I need for my garden?
Plant | Quantity | |
---|---|---|
Juglans nigra (Black Walnut) | N/A | Buy Plants |
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Becoming a contributing member of Gardenia is easy and can be done in just a few minutes. If you provide us with your name, email address and the payment of a modest $25 annual membership fee, you will become a full member, enabling you to design and save up to 25 of your garden design ideas.
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