Walnut poisoning is called Juglone which is a toxic compound that is found in all parts of plants of the walnut tree family Jugans, which is the toxic component.
The most common signs of walnut poisoning are moderate to severe laminitis, pitting edema of the distal portion of the limbs and a rapid respiratory rate.
Black walnut trees (Juglans nigra) produce a toxic substance (called juglone) that prevents many plants from growing under or near them.
Related trees like butternut (J. cinerea) and shagbark hickory (Carya ovata) also produce juglone, but in lower concentrations than black walnut.
Juglone cannot be easily neutralized – and it can persist in your soil for years, so even the most vigilant property owners may find this challenging.
Since juglone is present in all parts of the tree but is especially strong in the roots, which extend far beyond the canopy.
There is no cure for black walnut toxicity.
The best advice is to relocate your garden away from the tree.
If this is not possible, select tolerant species and take special care to minimize damage.