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):

Walnut

Family (Botanic):

Juglandaceae

Tree or Plant Type:

  • Tree

Foliage:

  • 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

Wildlife:

  • 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.

Location of Juglans nigra (Black walnut) at the Arboretum