Turning the crop of green rounded fruits on walnut trees into shellable walnuts involves work, but it's a satisfying way to get fresh walnuts for baked goods and munching. There are two kinds of walnuts, English walnuts native to Eurasia and black walnuts native to North America, and methods differ slightly for preparing each
Decide When to Harvest
Look at hull color and condition. For black walnuts, the hull goes from green to yellowish, and you can dent the hull by pressing with your thumb. In English walnuts, the hull begins to split away from the underlying shell. English walnuts usually start ripening September to November and black walnuts in August to September.
Crack open a few nuts to check for maturity and fullness. For English walnuts, test nuts from near the top of the tree since those ripen last. The membrane separating the two halves of the nutmeat should be brown rather than light-colored and the nut should fill out the shell. For black walnuts, check for full nutmeats, since in off years nuts can be shrunken or the shells empty and the nuts not worth harvesting.
Monitor the trees week by week to check for when nuts show the correct signs of ripening and maturity. For English walnuts, this should be when 95 percent of the hulls show signs of separating. For black walnuts, nuts should be harvested as they ripen over a period of weeks rather than all at once.
Pick the Walnuts
Nuts on lower branches can be picked by hand, but wear gloves. Nuts on higher branches can be knocked down with a pole. For English walnuts, put a hooked pole around higher branches and shake the fruits loose.
Gather fruits from the ground as soon as they are knocked from the branches. Do not let them stay on the ground, where they can be infested by insects and molds.
Put the nuts into plastic containers or sturdy disposable bags to take them to where they will be hulled.
Build an expanded metal screen, made by stapling a length of expanded metal to a frame built of 2x4 lumber. Decide on dimensions according to your work space. This is best for English walnuts.
Support the screen on sawhorses
Place English walnuts on the screen top and rub them back and forth. Hulls and other unwanted materials will fall through the screen, leaving the hulled nuts.
Place black walnuts on the ground, wear sturdy shoes, and trample on them. Use a firm soil or gravel substrate. Remove loosened hulls. Or soften hulls putting three parts unhulled nuts to one part water and one part gravel together in a container and stirring. Some people use this mixture in a cement mixer. Black walnut hulls are harder to remove than English walnut hulls.
Preparing for Storage
Wash the hulled nuts. This is best done outside.
Spread the nuts out in a single layer on a clean surface in a shady area to dry and cure, for English walnuts about three or four days. Crack a nut open to see if the nutmeat is still rubbery. If it is, longer drying time is needed. Cure black walnuts about two weeks. When completely cured, the nutmeat will snap when broken.
Store unshelled nuts in cloth bags or wire baskets at 60 degrees Fahrenheit or less until they are shelled. Provide good ventilation and a relative humidity around 60 percent for black walnuts, 70 percent for English walnuts. English walnuts keep for a year at 32 to 45 degrees Fahrenheit.