Gathering black walnuts for use is a three-step process that includes identification of the tree, harvesting the nuts and removal of the husk and shell. The husk and shell are difficult to remove and they stain anything with which they come into contact. Once the husk is removed, the shell needs to be cured for storage to avoid problems with mold. The meat of the nut can then be removed as needed.

Identification and Preparation

The black walnut tree is native to eastern North America and can be identified by its dark grey-brown bark with deep furrows and flattened ridges. The leaves are long and compound, about 12 to 24 inches, with alternating lance-shaped leaflets that are about 3 to 5 inches long. The nuts ripen in the fall and drop to the ground where they can be gathered. Straight from the tree they look like big green golf balls. It is best to wear old clothing and rubber gloves when working with black walnuts. You will also need a hard surface and an old pair of boots with hard soles, a hammer or a sharp knife to remove the husks. A five-gallon bucket or two can be useful to gather the walnuts into, and can be used once the husks are removed to soak the shells before using a wire brush to scrub them.

Harvesting

Harvesting of black walnuts can take place over a few weeks in mid-fall, once they start dropping from the tree. The best flavor is obtained by gathering them while the hull is still green and just starting to soften. They can be gathered even if the husk is black, but the juice is more likely to soak into the shell and change the flavor of the meat somewhat. You can knock the nuts from the tree as well as gathering them from the ground, but be careful not to break branches in the process. Wear the rubber gloves if you do not want your hands to be stained black for a few days or so. Bring a hammer to crack open a few and make sure that nut meat is present and fills the shell, you don't want to spend all the time required to process them just to find that the nut meat is lacking.

Processing

Once the nuts have been harvested, remove the husks. Spread them on a hard surface and grind off the husks with the sole of your boot, hitting them with a hammer or cutting a circle around them with a sharp knife and twisting them apart. Some people even drive over them with a car. Once the husks have been removed, put them in a bucket of water to soak. Later, use a wire brush and scrub each one to remove any remaining husk. Spread them on a drying rack to dry, in an area safe from squirrels. They will need to dry for a few weeks before you can move them to a storage bin. Store them in a cool, dry area for up to a year.

Source:

University of Minnesota Extension Service: Harvesting Black Walnuts

NatureSkills: Black Walnut Harvesting by JJ Murphy

Iowa State University: Harvesting, Cracking, and Storing Black Walnuts