Almost as well-known as its delicious nuts and its beautiful wood is walnut's toxic effect on neighboring plants. This effect has been known for millennia. Pliny the Elder wrote in the first century AD that, "the shadow of walnut trees is poison to all plants within its compass." Juglone, the toxin that the tree produces to keep the rest of the natural world at bay, is present in leaves, branches, bark, roots, and nuts. The chemical is toxic to a variety of other plants. Don't, for example, plant tomatoes near a walnut tree. The toxin's victims are not limited to plants. Bruised walnut leaves and branches have been put into water by fishermen to stun fishes.
(1) The American Heritage Dictionary of the English Language, Houghton Mifflin Company 2000. See the entry for Wales.
(2) Edward Goodell, Walnuts for the Northeast, Arnoldia 44: 1-19, 1984.
(3) The Romans' walnut was Juglans regia, Persian walnut. It is also called English walnut. But, as discussed above, there really is no such thing as an English walnut.
Copyright Gregory Palermo