With most trees, it’s best to let fallen leaves remain where they lie, but you can further reduce the concentration of juglone in the soil around a black walnut tree by keeping the area clean.

While producing this substance benefits the black walnut tree by limiting competition, it harms other vegetation, causing yellowed, wilted leaves and ultimately death from being exposed to juglone.

Some companies claim to sell black walnut tree clones developed at Purdue University; however, Purdue University no longer holds patent rights to these trees and cannot endorse the claims made for the ...