The Q&A Archives: Walnut Trees

Question: We live in Memphis, TN and our front lawn consists of Bermuda. Half of it anyway. The problem is that we have a walnut tree to the left side of our front yard. For some reason the only grass that will grow around the tree and that half of our yard is weeds. The bremuda won't spread. If we spray the yard, the weeds die, and then there is nothing but dirt.
Someone told my husband that the Walnuts are poisonous and when they drop on the ground they kill the grass.
Can you please tell me if this is true. And if so, what can we do about it. I would rather have the tree than the nice looking lawn, but I would like to also have a nice looking lawn. Half of it is beautiful, the other half looks terrible. Should we plant some other type of grass there, such as fescue?

Answer: Black walnut (Juglans nigra) has a reputation for being allelopathic--that is, for inhibiting the growth of other plants. Small amounts of juglone are released by the tree roots, but a far greater amount of this growth inhibiting chemical is found under the canopy of the tree.

Some plants are extremely sensitive to Juglone and others are quite tolerant. You might consider planting a groundcover rather than turfgrass. Ivy is tolerant of Juglone, as are Astilbe, Bee Balm, Bellflower, Bergamot, Ajuga, Coral Bells, Crocus, Shasta daisy, wild ginger, Lamb's ear, Lungwort, Morning Glory, Pansy, Phlox, Marigold, Primrose, Sweet Cicely, Honeysuckle and Zinnia.

Since your walnut tree is there to stay, try to plant one of the less-susceptible plants in the vicinity of the trees roots or canopy. Also, when planting under any tree, remember that feeder roots close to the surface of the soil will compete with the roots of other plants. As a result, you may have to water more frequently to keep the plants supplied with adequate moisture.

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