Emily's Gardening Almanac Timely Tips from a Professional Gardening Expert

Black Walnut Toxicity

The black walnut tree produces a chemical that can be toxic to other plants. This chemical is “juglone” which occurs in all parts of the black walnut.

“Juglone” is only slightly soluble in water and does not move very far in the soil. The greater quantities of “juglone” are present in the area immediately under the canopy of the black walnut. And because decaying roots still release “juglone,” toxicity can persist for some years after the tree has been removed.

Gardens should not be located near a black walnut tree. Leaves, barks, or wood chips of black walnut should never be used as mulch to gardens or the landscape.

Some of the more sensitive plants to “juglone” are:

cabbage, eggplant, pepper, tomato apple, blackberry, blueberry, saucer magnolia, rhododendron, and peony

Some plants tolerant of “juglone”:

Corn, lima beans, snap beans, onions, beets, winged euonymus, hawthorn, forsythia, pachysandra, most viburnums, virginia creeper, ferns, iris, trillium, shasta daisy, phlox, daffodil, fescue, Kentucky bluegrass.

Visit the following web sites for more gardening information and helpful tips:

Urban Horticulture, NCSU
Extension's Successful Gardener^sm

For informaton concerning this or other publications please contact Emily Revels, Extension Agent, Horticulture, at (910) 321-6870.

Created by Susan Johnson, System Administrator, May 2005