The tutor researches the effects of juglone from black walnut trees.

Juglone is a toxin produced by the black walnut tree; it’s found throughout the tree and in its leaves, shells and nuts.

Apparently, to humans eating the walnuts, the juglone is not a problem. However, it enters the soil from the roots of the black walnut tree, as well as from its leaves, twigs, and even pollen falling to the ground – not to mention the nuts and their shells. Some plants, such as tomatoes, potatoes, lilacs, and rhododendrons, can be damaged by the juglone.

To be safe, composted matter from black walnut should wait a year or more before application.

Horses are particularly sensitive to juglone; neither black walnut shavings, nor the husk fibre, etc, should be used in a horse’s environment.

Source:

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.