TREES & plants

Black walnut

The black walnut is a Chicago-area native tree that provides excellent shade for large properties. It needs to be sited with care, since the tree produces a chemical that is toxic to some other plants. The fruit is a rounded, yellow-green husk, containing a nut that is a food source for squirrels. The black walnut also attracts the banded hairstreak butterfly, serving as a caterpillar host.

Botanical name: 
Juglans nigra
All Common Names: 
Black walnut, Eastern black walnut
Family (English): 
Family (Botanic): 
Tree or Plant Type: 
  • Tree
Native Locale: 
  • Chicago area
  • Illinois
  • North America
Planting Site: 
  • Residential and parks
  • City parkway
  • Wide median
Landscape Uses: 
  • Specimen
  • Shade
  • Parkway/street
Size Range: 
  • Large tree (more than 40 feet)
Mature Height: 
50-75 feet
Mature Width: 
30-50 feet
Light Exposure: 
  • Full sun (6 hrs direct light daily)
Hardiness Zones: 
  • Zone 4
  • Zone 5
  • Zone 6
  • Zone 7
  • Zone 8
  • Zone 9
Soil Preference: 
  • Alkaline soil
  • Moist, well-drained soil
Acid Soils: 
  • Intolerant
Alkaline Soils: 
  • Moderately Tolerant
Salt Spray: 
  • Tolerant
Soil Salt: 
  • Intolerant
Drought Conditions: 
  • Moderately Tolerant
Poor Drainage: 
  • Moderately Tolerant
Planting Considerations: 
  • May be difficult to find in nurseries
  • Messy fruit/plant parts
  • Deciduous (seasonally loses leaves)
Ornamental Interest: 
  • Fall color
  • Edible fruit
Season of Interest: 
  • Early fall
Flower Color & Fragrance: 
  • Inconspicuous
Shape or Form: 
  • Round
  • Spreading
Growth Rate: 
  • Moderate
Transplants Well: 
  • Yes
  • Cavity-nesting birds
  • Game mammals
  • Songbirds
More Information: 

Tree & Plant Care

Falling fruit is a potential safety hazard and can cause yard litter as well as staining on sidewalks. 
Produces a chemical, juglone,  which is toxic to many plants.
Difficult to transplant due a deep taproot.
Do not prune in spring as black walnut is a 'bleeder' (sap will run from wounds).  Prune in dormant season.

Disease, pests and problems

Targeted by walnut and yellow leaf caterpillars.
Susceptible to anthracnose, which may lead to late summer defoliation.
Thousand canker disease is a serious problem occurring in some states (not yet reported in Illinois).

Black walnut (Juglans nigra)Black walnut (Juglans nigra)photo: John Hagstrom

Disease, pest, and problem resistance

Tolerant of high pH soil.
Shows some tolerance of salt.

Native geographic location and habitat

C-Value: 5
Native to much of the Eastern United States.

Bark color and texture

Bark is medium brown and has thick, interfacing ridges.

Leaf or needle arrangement, size, shape, texture, and color

Alternate, pinnately compound leaves with terminal leaflet often missing; leaf is 1 to 2 feet long; leaflets toothed; aromatic when crushed.
Leaves are green in summer, changing to yellow in fall.

Flower arrangement, shape, and size

Inconspicuous;  male flowers in drooping clusters; female flowers in terminal spikes.

Black walnut (Juglans nigra)Black walnut (Juglans nigra)photo: John Hagstrom

Fruit, cone, nut, and seed descriptions

Fruit is a yellow-green, rounded husk, up to 2 inches in diameter, containing an edible nut.