Black Walnut (Nigra)

The Black Walnut (Nigra) is generally described as a perennial tree. This is native to the U.S. (United States) has its most active growth period in the spring . The greatest bloom is usually observed in the late spring, with fruit and seed production starting in the fall and continuing until fall. Leaves are not retained year to year. The Black Walnut (Nigra) has a moderate life span relative to most other plant species and a rapid growth rate. At maturity, the typical Black Walnut (Nigra) will reach up to 100 feet high, with a maximum height at 20 years of 35 feet.

The Black Walnut (Nigra) is easily found in nurseries, garden stores and other plant dealers and distributors. It can be propagated by bare root, container, seed. It has a slow ability to spread through seed production and the seedlings have high vigor. Note that cold stratification is not required for seed germination and the plant cannot survive exposure to temperatures below -28°F. has low tolerance to drought and restricted water conditions.

Uses of : Landscaping, Medicinal, Culinary, etc.

Ethnobotanic: The bark of black walnut was used by many native groups, including the Cherokee, in tea as a laxative and chewed for toothaches. Caution: Bark should be used cautiously in medicine, because it is poisonous. The Cherokee also ate the fruit of the black walnut. The Chippewa and the Cherokee used the bark to make brown and black dyes. The Comanche created a paste from the leaves and husk of the fruit for treatment of ringworm. Black walnut was also used by the Appalachian, Cherokee, Comanche, Iroquois, and Rappahannock to treat athlete’s foot, hemorrhoids, and as an insecticide.

General Characteristics

General: Walnut Family (Juglandaceae). Black walnut is usually a medium sized tree ranging from 70-90 feet tall and 2-3 feet in diameter at breast height. However, black walnut can reach 150 feet tall and 8 feet in diameter at breast height. The branches are widely spread and form a massive crown. The bark is thick and brown to grayish-black in color. The bark has deep furrows and narrow forking ridges. The furrows and ridges form a diamond pattern. The twigs are stout with notched leaf scars. They are light brown to orangish in color. The terminal buds are short, blunt, and covered with a few hairy scales. The leaves are up to 6 dm long with 9-23 leaflets attached directly to a stout rachis without a supporting stalk. The rachises are covered with fine short hairs. Flowers appear in late May to early June. The flowers bear 17-50 stamens, but lack pistils. The fruits are 4-6 cm in diameter and spherical shaped. They can be found in groups of 2-3 or solitary. The fruits have a thick, semi-fleshy, husk covered with short hairs and are yellowish-green in color. The nut is corrugated with rounded ridges.

Required Growing Conditions

For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Habitat: Black walnut is found in fields and rich woodlands.

Adaptation Black walnut produces a toxin, known as “juglone”, which inhibits the growth of other plants around it, thereby reducing competition. Juglone deprives sensitive plants of energy needed for photosynthate production. The symptoms of plants being affected by juglone include foliar yellowing, wilting, and eventually death. The largest sources of juglone on the tree are located in the buds, roots, and nut hulls.

Cultivation and Care

Black walnut is difficult to transplant and therefore, propagation by seed is recommended. Seeds should be planted in the fall in moist, well-drained, deep soil that is rich in organic matter. Black walnut prefers full sun.

General Upkeep and Control

Black walnut is a very intolerant tree. Planted in fairly dense stands or under forest competition the tree develops a tall and well formed clear bole. This bole form results from the tree putting its resources into competing for sunlight and is ideal for wood fiber production. Logs 10 inches in diameter at breast height can be developed in 35 years under ideal growing conditions.

Pests and Potential Problems Black walnut suffers from a variety of deforming and deadly pests and diseases including parasitic nematodes, mistletoe, fusarium canker, bacterial blight, white trunk rot, and cylindrockadium root rot.

Environmental Concerns Juglone may be a concern when landscaping or planting black walnut near a garden.

Plant Basics
Growth Rate Rapid
General Type Tree
Growth Period Spring
Growth Duration Perennial
Lifespan Moderate
Plant Nativity Native to U.S.
Commercial Availability Routinely Available
Physical Characteristics
Bloom Period Late Spring
Displays Fall Colors No
Shape/Growth Form Single Stem
Drought Tolerance Low
Shade Tolerance Intolerant
Height When Mature 100
Vegetative Spread None
Flower Color Yellow
Flower Conspicuousness No
Fruit/Seed Abundance Low
Fruit/Seed Seasonality Fall Fall
Seed Spread Rate Slow
Gardening Characteristics
Propagations (Ways to Grow) Bare Root, Container, Seed
Moisture Requirements High
Cold Stratification Required No
Minimum Temperature -28
Soil Depth for Roots 40
Toxic to Nearby Plants Yes
Toxic to Livestock No
After-Harvest Resprout Ability Yes
Responds to Coppicing No
Growth Requirements
pH Range 5.5–8 pH
Precipitation Range 30–30 inches/yr
Planting Density 100–800 indiv./acre
Soil Textures Medium
Soil Depth for Roots 40
Minimum Frost-Free Days 170 day(s)
Salinity Tolerance None
CaCO3 Tolerance High
Sustainability & Use
Leaf Retention No
Palatability Low
Fire Resistant No
Causes Livestock Bloating None

Source: USDA, NRCS, PLANTS Database,
National Plant Data Center, Baton Rouge, LA 70874-4490 USA