How long do Black Walnut roots give off the toxin after the tree is cut down?

Question:

Answers:
After cutting down a walnut tree there is still juglone, unless all roots are removed from the soil. This gets to be a tedious and complex job (feeder roots are very tiny). Any roots remaining in the soil can continue to give off the toxin juglone, until the roots deteriorate and decay (sometimes several years).