TREES & plants

Black walnut

A mature black walnut tree.

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. 

This species is native to the Chicago region according to Swink and Wilhelm's Plants of the Chicago Region, with updates made according to current research.

Botanical name: 
Juglans nigra
All Common Names: 
Black walnut, Eastern black walnut
Family (English): 
Family (Botanic): 
Tree or Plant Type: 
  • Tree
  • Deciduous (seasonally loses leaves)
Native Locale: 
  • Chicago area, 
  • Illinois, 
  • North America
Planting Site: 
  • Residential and parks, 
  • City parkway, 
  • Wide median
Landscape Uses: 
  • Parkway/street, 
  • Shade tree, 
  • Specimen
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 (Chicago), 
  • 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
Ornamental Interest: 
  • Fall color, 
  • Edible fruit
Season of Interest: 
  • Early fall
Flower Color & Fragrance: 
  • Inconspicuous
Shape or Form: 
  • Round
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.

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

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

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

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.

Fruit, cone, nut, and seed descriptions

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

Juglans nigra or Black walnut