Q: I read recently about walnut toxicity. There is a black walnut tree twenty feet from my garden and some of the leaves are in my compost, maybe 5% – 10%. Will I be able to use it in my vegetable garden next year?
A: With only a 5% – 10% concentration, I don’t think you have much to worry about. The majority of the walnut’s plant-harming chemicals are in the roots. The process of composting does a good job breaking down the compounds that might be present.
see Walnut Leaves