Toxic Parts:
Flower Color:
  • flower color
  • flower color
meadows, woodlands, ornamental, gardens

Time of Greatest Risk


Geographical Distribution

Black walnut  distribution - United States

Black Walnut

Juglans nigra

8/ 10
Black walnut (Juglans nigra) is a large deciduous tree with long trunks, often with an absence of lower branching. Leaves are strongly aromatic when crushed, late to emerge in the spring, and early to drop in the fall once yellowed. Yellow-green flowers blossom in late spring which produce nuts encased in yellow green, slightly hairy husks which hang in drooping clusters of 1-3. The wood from J. nigra is highly valued for a number of commercial uses including cabinets, furniture, gunstocks and fine veneers.

Toxic components
The bark, woods, nuts, and roots of J. nigra contain juglone, a compound which is toxic to horses. Horses are primarily affected by exposure to shavings containing parts of the black walnut tree. Horses can also be poisoned from ingestion of the bark, pollen, or fallen leaves. The toxic chemical responsible is called juglone, which is contained at high concentrations in the bark and wood and lower but still toxic amounts in the leaves. Symptoms usually disappear within hours after the horse is removed from the shavings; however, laminitis can present further problems.


  • Edema Of The Lower Limbs
  • Laminitis
  • Elevated Temperature
  • Increased Respiration Rate
  • Increased Digital Pulse And Hoof Temperature
  • Depression
  • Abdominal Sounds


MECHANICAL CONTROL: Cutting down and removing the tree is of limited help unless the roots are also removed from the soil.