The symptoms of juglone poisoning include yellowing or browning of the leaves of affected plants, stunted, twisted growth or a failure to grow, sudden wilting, and death. As walnut and butternut trees grow larger and their roots spread, sensitive plants further and further away from the main trunks of these trees will begin to decline in health and may eventually die.
Not all plants are affected by this toxicity problem. Some plants have a natural resistance to juglone and can survive near and even under walnut and butternut trees. Some plants do not grow deep roots, and more shallow root systems seem to be more resistant as well. Juglone is present in all parts of black walnut and butternut trees. Care needs to be taken when disposing of the nuts, bark, and leaves of these types of trees. Do not use these materials for mulch around plants that are not tolerant of juglone.