Black walnuts have a distinctive flavor and make a marvelous addition to breads, cakes and other baked goods. If you are lucky enough to have access to a black walnut tree (Juglans nigra, also called the American walnut), you can reap a large harvest of the nuts each fall. By freezing what you don't use right away, you are ensured a plentiful supply of nuts for future use.
Harvest the nuts periodically as soon as the tree begins dropping them over a four- to six-week period. Keep them in a box or bushel basket until you are reading to hull them. Squirrels love black walnuts, so be sure to store them in a spot squirrels cannot reach.
Rub off the husk using your hands or the side of a hammer. Husks start off green, but turn black with time (this doesn't mean the nuts are bad). Be sure to wear heavy gloves and protect your work surface when you remove the husks, because the husks contain a deep brown dye that stains.
Rinse the nuts. It is best to do this in a utility tub, or outside with a garden hose, because more of the stain will rinse off them. Allow the nuts to dry, then store them for curing.
Cure the nuts by stacking them in shallow layers no more than two or three nuts deep. Keep them in a cool, dry, well-ventilated place, out of direct sunlight, for two weeks. The curing time allows the nuts to develop their flavor.
Break open a sample nut after the curing time. You will know the nuts are ready to open if the kernel breaks crisply with a sharp snap.
Moisten the nuts when you are ready to shell them, to help keep them from shattering. Soak them in hot water for 24 hours, then drain the water and soak them again for two hours. Keep the nuts moist by covering them with a damp cloth until you shell them.
Shell the nuts. Even after soaking, the shells are very hard, and may not yield to the force of a nutcracker. Placing the nut in a vise and carefully applying pressure until the shell cracks is a quick method of removing the shell from the nutmeat.
Discard the shells and store shelled nuts in a tightly closed container or sealed plastic bag in the refrigerator for up to nine months. The nutmeats can also be frozen for up to two years.