- Black walnut trees produce popular edible nuts, but some plants cannot grow near them.walnut image by RT from Fotolia.com
Black walnut trees are grown for their edible nuts, useful hardwood, shade and attractiveness in a landscape. The trees grow relatively easily but can affect other plants. Gardeners should carefully choose where to plant black walnuts, because Purdue University Horticulture warns that they produce a chemical that kills some plants. This chemical, called "juglone," does not spread out very far in soil but does enter the soil near black walnut tree roots.
- Tomatoes and a few other vegetables cannot grow near black walnut trees.tomato #2 image by Adam Borkowski from Fotolia.com
Several vegetables do not tolerate the juglone from black walnut trees. Tomato plants, asparagus, peppers, potatoes and eggplants do not grow well near black walnuts, according to Ohio State University, the Morton Arboretum and Purdue University Horticulture. Ohio State University explains that these plants cannot grow within 50 feet of a black walnut tree's drip line.
- Blackberries will die if gardeners plant them near a black walnut tree.blackberries image by L. Shat from Fotolia.com
Black walnut toxicity kills some fruit plants, including blackberries, blueberries, pear trees, crabapple trees and apple trees, according to Purdue University Horticulture and Ohio State University.
- Norway spruce trees die from black walnut toxicity.spruce image by DOLPHIN from Fotolia.com
Several tree varieties are among the plants affected by black walnuts. Mugo pine trees, red pine trees, white pine trees, silver maples, hackberry trees, white birch trees, European alder trees and Norway spruces cannot grow near black walnuts. Since tree roots often spread out relatively far in the ground, gardeners may want to plant these trees a little bit more than 50 feet from a black walnut tree's drip line.
Flowers, Shrubs and Perennials
- Hydrangeas and a few other flowers do not grow near black walnut trees.hydrangea image by L. Shat from Fotolia.com
Purdue University Horticulture, Ohio State University and the Morton Arboretum warn that rhubarb, lilies, tobacco, columbine, some peonies, hydrangea, most rhododendrons, some narcissus, honeysuckle, cinquefoil, chokeberry, red laurels, yew and lilacs die from the black walnut's chemicals in the soil. Ohio State University explains that peonies, viburnum plicatum tomentosum and chrysanthemums might grow near black walnut trees but will not grow as well near them as they would grow away from the trees.