Common Walnut

“A Low-Maintenance and Frost-Hardy Tree”

The walnut is a deciduous tree with bark that changes from green-brown when young to pale and fissured when mature. It was introduced by the ancient Romans, who believed the edible nuts were the food of their god Jupiter. Walnut wood is prized for woodworking and gun stocks. The wood at the base of the tree is especially valued for its beautiful swirling grain patterns. The leaves and mature fruit yield a dark brown dye.

Common walnut

Culture

  • Grows slowly to more than 12 m; the canopy can reach wider than 8 m
  • Low maintenance and frost-hardy
  • Grows best in full sun, on well-drained, fertile soils. It is tolerant of most soil types and pHs, but prefers slightly alkaline soils
  • Walnuts naturally release chemicals that can hamper the growth of other plants, especially those below them

Concerns

  • Aphids can be an issue
  • Susceptible to honey fungus (Armillaria)
  • Walnut leaf blotch causes small brown spots that merge into blotches, sometimes with yellow margins
  • Generally cosmetic issues such as coral spot, white leaf spot, or galls on the leaves
  • Rarely, bacterial leaf blight causes small brown spots on leaves and affects fruit

Bartlett Management Practices

  • Inspect the base of the tree for peeling bark with mycelial fans/rhizomorphs beneath
  • If honey fungus is present, we ensure the tree is unstressed to reduce susceptibility and remove any sources of infection as far as possible
  • Excavate buried root collars
  • Check for aphid symptoms: curling leaves and honeydew
  • For leaf spot, remove and destroy fallen leaves. In severe cases we apply an appropriate fungicide
  • Prune out and destroy coral spot material, sterilising equipment between branches

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