Content Detail

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.

  • Family (English) Walnut
  • Family (botanic) Juglandaceae
  • Planting site City parkway, Residential and parks, Wide median
  • Tree or plant type Tree
  • Foliage Deciduous (seasonally loses leaves)
  • Native locale Chicago area, Illinois, North America
  • 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 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
  • Soil preference Alkaline soil, Moist, well-drained soil
  • Tolerances Alkaline soil, clay soil, Occasional drought, Road salt
  • Season of interest early fall
  • Flower color and fragrance Inconspicuous
  • Shape or form Round
  • Growth rate Moderate
  • Transplants well Yes
  • Planting considerations May be difficult to find in nurseries, Messy fruit/plant parts
  • Wildlife Cavity-nesting birds, Game mammals, Songbirds
  • Has cultivars Yes

Native geographic location and habitat:

Black walnut is native to much of the Eastern United States. C-Value: 5.

Bark color and texture:

The bark is medium brown and has thick, interfacing ridges. 

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

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

Flower arrangement, shape, and size:

The flowers are inconspicuous. The male flowers are in drooping clusters and the female flowers in terminal spikes.

Fruit, cone, nut, and seed descriptions:

The fruit is a yellow-green, rounded husk, up to 2 inches in diameter, and contains an edible nut.

Plant care:

Falling black walnut fruit is a potential safety hazard and can cause yard litter as well as staining on sidewalks. All parts of the tree produce a chemical, juglone, which is toxic to many plants. The trees are difficult to transplant due to a deep taproot. 

Do not prune in spring as black walnut is a ‘bleeder’ (sap will run from wounds). Black walnut should be pruned in the dormant season.

List of pests and diseases:

Black walnut is targeted by walnut and yellow leaf caterpillars. It is 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). It is tolerant of high pH soil and shows some tolerance of salt.


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