Laidback Gardener Tip of the Day

Yes, You Can Compost Black Walnut Leaves

20151015ABlack walnut (Juglans nigra) and, to a lesser extent, other walnuts (Juglans spp.), as well as their close relatives, the hickories (Carya spp.), release a product called juglone that is allelopathic, that is to say toxic to most other plants. Thus, the walnut suffers little from competition, as few other plants can grow well at its base (here’s a list of plants that are resistant to juglone). Juglone is present in all parts of the walnut tree except the nut itself: leaves, branches, bark, wood, and especially its roots and nut husks.

The question is therefore: should the home gardener put “toxic” black walnut leaves in their compost bin? Ohio State University looked into the matter and the reply is yes: juglone decomposes within weeks in contact with air, water and bacteria. If the leaves are finely shredded, decomposition is even quicker. And once decomposed, walnut leaves apparently give a compost of excellent quality.

Walnut sawdust and wood chips as well as walnut husks, however, are slower to decompose: it is best to compost them for 6 months before using them in the garden to be sure the juglone has thoroughly decomposed.

Garden writer and blogger, author of more than 60 gardening books, the laidback gardener, Larry Hodgson, lives and gardens in Quebec City, Canada. The Laidback Gardener blog offers more than 2,500 articles to passionate home gardeners, always with the goal of demystifying gardening and making it easier for even novice gardeners. If you have a gardening question, enter it in Search: the answer is probably already there!

1 comment on “Yes, You Can Compost Black Walnut Leaves

  1. Pingback: Yes, You Can Compost Poisonous Leaves | Laidback Gardener

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