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Black WalnutJuglans nigra

  • Black Walnut - Juglans nigra
  • Black Walnut - Juglans nigra
  • Black Walnut Juglans nigra
When grown in the open, the black walnut reaches 75' tall with a round, low branching, open crown that spreads nearly as wide as it is tall. In forests and plantations, the tree may reach 150' tall with a well formed trunk and lower limbs self pruned from « to 2/3 the distance from the ground. It develops a deep taproot and is difficult to transplant. The hard to crack shell encases a rich flavored nut. However, the crushed black walnut shells can stain fingers, clothing, and concrete. The trees bear in 12-15 years. (Partally self-fertile, plant multiple trees to ensure pollination) (zones 4-9) Alleopathy is the term given to the suppression of growth of one plant species by another due to the release of toxic substances. Black walnut tree roots contain juglone, a toxic substance released when the the roots of other juglone-sensitive species come in contact with walnut roots. You must keep a wide separation between the black walnut tree and susceptible plants. A partial list includes tomatoes, potatoes, peas, peppers, cabbage, alfalfa, serviceberry, chestnut, pine, arborvitae, apples, blueberry, blackberry, cherry, azalea, rhododendron, lilac, hydrangea, privet, members of the heath family. The black walnut's poison does not work on all species and some even seem to thrive on it.

Hardiness Zones

The black walnut can be expected to grow in Hardiness Zones 4–9. View Map

Tree Type

Mature Size

The black walnut grows to a height of 50–75' and a spread of 50–75' at maturity.

Growth Speed Medium Growth Rate

This tree grows at a medium rate, with height increases of 13–24" per year.

Sun Preference

Full sun is the ideal condition for this tree, meaning it should get at least six hours of direct, unfiltered sunlight each day.

Soil Preference

The black walnut grows in in acidic, alkaline, loamy, moist, rich, sandy, well-drained, wet and clay soils.

Attributes

This tree:
  • Yields a ripened nut crop in early to mid-autumn. The fruit consists of three layers: a green, fleshy husk; a black inner shell that is hard, thick and corrugated; and the kernel, which is oily and sweet.
  • Begins to bear nuts in 12–15 years.
  • Is prized in the woodworking world for its handsome grain.
  • Features pinnately compound, alternate leaves that are 12–24" in length and consist of 15–23 dark green leaflets that are 2–5" long. The leaflets are finely toothed.
  • Is self-fertile but requires wind for pollination. Plant more than one tree to ensure a better crop.
  • Grows in a rounded shape.
  • Develops a deep taproot, making it difficult to transplant.
  • Can be toxic to certain trees and plants--such as serviceberries, chestnuts, pines, arborvitae, apples, cherries, tomatoes, potatoes, peas, peppers, cabbages, alfalfa, blueberries, blackberries, azaleas, rhododendron, lilacs, hydrangeas, privets and plants in the heath family--if planted too close.

Wildlife Value

The nuts are eaten by woodpeckers, foxes and squirrels.

History/Lore

This native tree has been called our best friend in times of war and peace. Native Americans and early settlers used it for food, dyes, ink, medicine, fence posts, gun stocks and furniture.