Can I use woodchips from walnut as mulch in my landscape?
Can I use woodchips from black walnut as mulch in my landscape?
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 leaf litter, fallen fruit, or mulch created from black walnut.
You can use chips or mulch produced from black walnut in landscaping. Juglone is present in very small amounts in leaves, stems, and wood. Additionally, juglone breaks down quickly in the soil. Any damage to plants presumed to be caused by mulch derived from walnut trees is more likely due to other mulch conditions that can happen with mulch derived from any tree species (like oxygen depletion, sour mulch, etc.) rather than juglone.
Learn more about juglone and its limited impact on garden plants in this article: Do black walnut trees have allelopathic effects on other plants?
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