I keep planting flowers around my black walnut tree, and they keep dying. What’s the problem?
Black walnut is what’s known as an allelopathic plant, which means it contains a natural poison that kills or interferes with the growth of nearby plants. Black walnut leaves and wood, and especially the roots, contain a powerful chemical called juglone.
Juglone is harmful to many garden plants such as nightshade vegetables, azaleas, rhododendron, blueberries, and petunias. Juglone can stay in the roots and soil for years after the tree is cut down, and it’s also present in fallen leaves, debris, and water runoff.
Allelopathy is a sort of quiet chemical warfare that beats out the competition – which is great if you’re a walnut tree, but not so great if you’re trying to garden near one! If you have a black walnut tree in your yard, here are some tips for dealing with its allelopathic traits:
- Keep Plants Healthy: Weakened plants are more susceptible to allelopathic chemicals, so make sure your garden plants are in good soil and are healthy.
- The Walnut Tree: Allelopathic Effects and Tolerant Plants (Virginia Tech)
- Allelopathic Plants: Nature’s Weedkiller (Earth Friendly Gardening)
- Allelopathy: How Plants Suppress Other Plants (University of Florida)