Unripe walnut tree growing in orchard
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Can Walnut Trees Really Wipe Out Nearby Plant Competition?
The myth that nothing grows underneath a walnut tree seems to be far from baseless, as these trees release a potent chemical called juglone through their roots, hulls, and leaves.
This toxin harms many plants dominating American gardens, including fruits and vegetables like tomatoes, blueberries, and apples, and flowers like azaleas, petunias, and peonies.
These plants physically suffer and are kept from growing to their full potential, as exposure to juglone negatively impacts their respiratory systems. At worst, they could die.
However, a few plants find juglone bearable and may appreciate the shade these trees offer — for instance, carrots, beets, onions, squash, and select types of beans.
Plus, a variety of other trees and flowers aren't as sensitive to the walnut tree's harmful effects, including oak trees, poplars, red cedars, marigolds, pansies, and zinnias.