If you have access to a black walnut tree and enjoy the nuts raw or in baked goods, you will need to care for them properly until you are ready to use them. Black walnuts are typically harvested in the late summer or in the fall, depending on your climate. You can pick them directly from the tree or harvest from the ground, as long as you get them before the squirrels and other animals do.
Husk black walnuts before you store them, since the husk will ruin the nut's flavor. Hammering the sides of the nuts can remove the husks. This is a messy process, and the dye from the husks can stain your hands, clothes and counter, so take preventative steps such as wearing safety glasses, gloves and old clothes. Do not place the husks in your compost bin. They are toxic to many plants.
Leave the shells, which are under the husks, intact for storage. Wash the shells outdoors to avoid staining your sink. Again, wear old clothes and gloves to avoid staining.
Place the nuts a handful at a time in a bucket of water. The nuts that float have insect damage and should be thrown out. Those that sink are good enough to store.
Cure--or dry--the black walnuts. Stack the nuts two to three layers deep on trays. Stick them in a cool, well-ventilated location that is out of direct sunlight, such as in your garage. Leave them there for two to three weeks. They are dry when the kernels inside the shell give a sharp snap when broken.
Store the nuts in wire baskets, mesh bags or cloth bags. Set them in a well-ventilated area with temperatures around 60 degrees F and a relative humidity level around 70 percent.
Check on the nuts periodically to be sure they are not cracking and mold is not growing. If they are cracking, the area you have them in is probably too dry. If they are molding, they are not getting enough air circulation. Remove the moldy walnuts and try a different storage method, such as in wire baskets instead of cloth bags.