How long does juglone last in the landscape after the removal of a walnut?


How long does juglone last in the landscape after the removal of a black walnut?


Black walnut (Juglans nigra) is a common woodland and landscape tree in the Midwest. 

Much has been written about the allelopathic properties of black walnut.  When plants produce a chemical that prevents the growth of other plants, it is called allelopathy. Black walnut produces juglone which can cause an allelopathic response (inhibition of growth) in other plants. Other members of the Juglandaceae family (including butternut and pecan) also produce juglone, but black walnut produces more than other members of the family. 

Very little research has been done to show that juglone causes damage to plants near black walnuts or near the root system, stump, leaf litter, fallen fruit, or mulch created from black walnut. 

Juglone is present in very small amounts in leaves, stems, and wood.  Additionally, juglone breaks down quickly in the soil, so in just a few months after removing the tree, most of the juglone is gone.  It is safe to replant the next growing season in spaces formerly occupied by walnuts. 

Learn more about juglone and its limited impact on garden plants in this article: Do black walnut trees have allelopathic effects on other plants?

Answered by
  • Specialist
  • Consumer Horticulture Extension
Last updated on
March 20, 2024