Q: Are pecan leaves good to mulch a garden? The local Cub Scout pack will be raking leaves at our church and I was planning to put them on our community garden there. 

A: It’s well-known that juglone, a chemical in walnut leaves and roots, can interfere with plants growing underneath. All members of the walnut family (hickory, pecan, etc) exude varying amounts of juglone. But it ‘s hard to predict how much juglone is in your pecan leaves. Amounts vary by variety, weather, and time of year. My bet is that is there’s not much bad stuff there but I’m not sure I want to say the leaves are completely safe to use on the garden.The chemical would be degraded by composting the leaves but how long would it take to get it all out? I guess it’s better to be safe and not use the leaves on the garden beds.

Occurrence of Juglone in Pecans

Potential allelopathy in different tree species