Planting Under Black Walnut Trees
We’re often asked about planting under Black Walnut trees, as the trees present a unique challenge for gardeners. Black Walnut trees produce a chemical called hydrojuglone, which is found in the leaves, stems, fruit hulls, inner bark and roots. When exposed to the air or soil, hydrojuglone is oxidized into the chemical juglone. Juglone is toxic to numerous plants, but many native plants are resistant to the toxins.
Soil that is compacted, slow draining, or lacks sufficient healthy microbial growth, will have less success supporting plants under Black Walnut trees.