The black walnut (Juglans nigra) is one of the most valuabletimber trees in Iowa. It is also a valuable nut tree.
Walnuts ripen in the fall. As the fruit matures, the hullsoftens and changes from a solid green to a yellowish color. Thefruit are mature and ready for harvest as soon as the hull can bedented with your thumb. The best quality nuts are obtained bypicking or shaking the mature nuts from the tree. Mostindividuals, however, gather the mature nuts as they drop to theground. Dropping of mature nuts usually occurs in mid to lateSeptember. Before you spend a lot of time gathering nuts, it's agood idea to crack a few to make sure the kernels are full. Nutsoccasionally fail to fill or have small, shrunken kernels. Nutcrops vary from year to year. A tree that produced bushels lastyear may have many or few nuts this year.
The nuts should be hulled immediately after they have beenharvested. If the hulls are allowed to remain on for any length oftime, the juice in the hull will discolor the nut meats and makethem strong tasting. The stain also discolors skin, clothing,concrete, and anything else that it touches. There are variousways and devices to hull walnuts -- a cement mixer, corn sheller,automobile wheel, and squirrel cage are possibilities. Hulls canalso be removed by stomping the nuts under foot or pounding with ahammer. After hulling, thoroughly wash the nuts to remove hulldebris and juices. Small quantities can be washed in a largebucket or tub. At this time, the good nuts can be sorted from thebad ones. Unfilled nuts float while filled nuts sink. (Rubbergloves should be worn when hulling and cleaning to prevent stainingof the hands.)
After washing and sorting, allow the nuts to dry for two orthree weeks. An excellent way to dry nuts is on a wire screen. Spread the nuts in shallow layers (no more than three nuts deep)and dry them in a cool, dry, well-ventilated area. A shed orgarage is usually a good place to dry walnuts.
The black walnut has one of the toughest and thickest shellsto crack. While nuts can be cracked with a variety of tools, thehammer and nutcracker are most commonly used. The hammer methodinvolves placing the nut, pointed end up, on a hard surface andstriking the point with the hammer until it weakens and splits intosections along its axis. Several nut cracking tools are alsoavailable. When cracking nuts, shattering of the kernels is oftena problem. Shattering can be reduced by soaking the nuts in waterfor 1 or 2 hours before cracking. The soaking process allows thekernels to absorb enough moisture to become somewhat flexible,resulting in larger kernel pieces. The kernels are extracted fromthe nutshell with a pick and a pair of pliers.
The oils in walnut kernels will turn rancid if nuts are storedimproperly. After the kernels have been removed, place them in aplastic bag and store in the freezer. The nut meats will keepalmost indefinitely when stored in the freezer. Kernels can bestored for short periods in the refrigerator.
Harvesting, hulling, cleaning, and cracking black walnutsrequires considerable labor and patience. Those efforts, however,are rewarded when fudge, brownies, candies, and cakes are made fromIowa-grown black walnuts.
This article originally appeared in the September 16, 1994 issue, p. 142.