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.
The bark, woods, nuts, and roots of J. nigra
contain juglone, a compound which is toxic to horses. Horses are primarily effected 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.