The husk of black walnuts leaves a greenish dye that is commercially very useful for dying textiles but is not good for your hands. Put on gloves before you start handling the walnuts because this dye is very stubborn and may take days of scrubbing to leave you.
The peak harvest time is September/October when the walnuts are fully ripe. You can judge the ripeness with the touch of the husk. If it is soft than the nut is ripe. If it is hard and stubborn, then the tree probably needs some more time to ripen up. Place a large piece of cloth under the walnut tree and shake a branch that contains ample quantity of the fruit. Collect the walnuts that fall underneath.
Now is the time to take off the husk. It is best done by laying the walnuts on a driveway and rolling the board over it. This crushes off the husk, leaving behind the walnuts. Use your feet to apply pressure over the board to remove the husk. Now use your hands to free the walnuts of the husk skin and collect them in a bucket.
Wash the walnuts and let them dry in the sun. If you do not dry them well, they will rot. You can now store the walnuts for a long period of time. When you want to eat the meat, use a nut cracker or hammer to smash the shell and get the meat out.