Black walnuts grow on trees throughout the Midwest. These nuts, known for their dark shells, are easy to harvest but can be tough to crack. You'll want to make sure you have a nutcracker specifically designed to handle black walnuts before harvesting them. Wearing gloves while handling the nuts is also very important. The dark substance on the shell can stain the skin, as well as any clothes it comes into contact with.
Black walnuts are usually ready to harvest in the fall. Depending on where you live, this can be anytime from September through November. It's usually easy to tell when the nuts are ripe because they will start falling from the tree.
Maturing black walnuts will change in appearance as they grow nearer to harvest time. The round, smooth hull will start out a bright shade of green. As the nut ripens, the hull will take on a yellowish hue with black splotches. The nut is ready to harvest when you can dent the hull with your thumb.
Another clue that the nuts are ready to harvest is when they begin to drop to the ground. It is fine to collect these nuts, as long as you do so as soon as possible. You can also pick ripened black walnuts directly from the tree.
Make sure to pick and test several nuts before harvesting the whole batch. Sometimes black walnuts that appear to be ripe need a bit more time. To test the nuts, crack open three or four to make sure the kernels are full and mature. If they are shrunken, you may want to wait a few more days and test a new batch. Waiting may not help; sometimes, trees just have a bad year and fail to produce good nuts.
Process the ripe nuts immediately after you pick them. Dye from the hulls can seep into the harvested black walnuts, rendering them discolored and bitter.