Can you compost black walnut hulls?
The mention of black walnut trees makes many gardeners groan, because all of the plants parts, from leaf to root tip, contain a substance called juglone that causes severe stunting of many plants, including tomato. In fall, black walnut hulls become a car-bashing, foot-bruising problem, too. After you harvest the nuts, you're left with that pile of tarry hulls. Is it really safe to compost them?
Thanks to on-farm research done by Chris Chmiel in Athens, Ohio, the answer is yes. Looking at all the wasted hulls from black walnut processors in his area, Chmiel launched into a three-year study that showed that a year of composting turned walnut hulls into a soil amendment with some surprising properties – such as an alkaline pH instead of an acidic one.
Best known for championing the culture of native paw-paw trees, Chris Chmiel grows paw-paws, goats, and makes compost at Integration Acres in Ohio.
— Barbara Pleasant, contributing editor and author of The Complete Compost Gardening Guide