Walnut trees are beneficial to a landscape for their nut harvest, moderate shade and foliage. The downside of growing a walnut tree is that not many companion plants do well nearby because of the juglone toxin produced by the walnut tree. In the past there has been some debate as to whether you can compost the walnut leaves or not, but it has been proven that you can compost the leaves with other items in a compost pile.
Layer the walnut leaves into the compost pile. Begin with a layer of walnut leaves, then a layer of grass clippings and then a third layer of organic materials such as eggshells or fruit and vegetable matter. The pile needs to be at least 6 inches deep. Alternate with these layers while building the compost pile.
Turn the compost pile each week to provide adequate air circulation and moisture. Use a shovel to sift materials from the bottom up to the top. Mix it thoroughly.
Keep the compost pile moist. To see if there is enough moisture, pick up a handful and squeeze it. If no moisture seeps out, it needs more. Sprinkle with water, and turn with the shovel again.
Add more grass clippings if the compost pile begins to smell badly. You want the compost pile to smell of earth more than anything else.
Let the walnut leaf degrade in the compost (while being turned with the shovel weekly) for at least a month. It takes four to six weeks for the juglone toxin to break down in the walnut leaves. When it is ready to use, compost should feel crumbly and have an earthy smell.