Everyone loves black walnut (Juglans nigra) for its timber, but it’s also a valuable nut tree. It’s an American native tree that may look like it’s the common walnut, but as far as I am concerned, the taste is completely different.
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Black walnuts ripen in the fall. Watch for the husks on the fruit to change in color from a medium green color to a yellow-green. You’ll know they’re ready for harvesting when the husks soften enough that you can put a dent in it by pressing hard with your thumb. A word of caution, the smell can be a bit overpowering at first, but you quickly get used to it.
To get the best quality, pick or shake the mature nuts from the tree. You can also gather them from the ground but you’ll need to act fast as the squirrels quickly gather and store them for their winter food. Black walnut trees begin to drop their fruit in mid to late September but can be as late as October, all depending on where you live. Remember, nut crops can vary from year to year. Some years may produce small thin nuts that aren’t worth harvesting, and other years the crop can produce nice meaty nuts. It’s a good idea to crack a few before spending time harvesting baskets full.
Hull your black walnuts as soon as possible after you harvest them. If you wait, the hull will turn dark and the juice will leak into the nut and cause discoloring of the meat as well as give them a very strong flavor. The juice will also stain just about anything it touches. Always wear old clothes and gloves when you are hulling black walnuts because it does get messy! The way I have learned to the hull was by placing them on the ground (I do this right under the tree) and walk or stomp on them until the hulls fall off. Using a hammer also works. I have heard that you can also use devices like a cement mixer or corn sheller. When the hulls are removed, scrub the nuts well in a bucket of cool water to remove the remaining hull and dye. If a nut floats to the top of the water, discard it as the meat is either not developed or has insect damage.
You can compost the hulls but it’s tricky. They contain juglone which is toxic to many garden plants hence it is generally avoided to grow tomatoes, cabbage, peppers, eggplant, and potato as they are juglone-sensitive. The juglone toxicity degrades over 2 to 4 weeks. It may take up to two months to break down in the soil. The bark takes a minimum of 6 months to compost to yield a safe mulch. You can even use that for plants sensitive to juglone.
Now it’s time to let the black walnuts dry or cure. The best way to do this is on a wire screen for 3 to 5 weeks. Spread the nuts out so they are no more than 2 layers deep and place them in a cool, dry, well-ventilated area. A shed or a garage work well as long as squirrels can not find their way in.
Now it’s time to crack them. The black walnut has an amazingly thick shell. You can use a nut cracker, but a hammer or even a vise works best. They seem to crack easier if they are soaked for 1 to 2 hours before cracking them. This also helps prevent the shattering of the kernel when the shell breaks. If you use a hammer, set the nut so it’s pointed side is up and smack it until it splits into sections.
If you’re not using the meat right away, store the kernels in a plastic bag in the freezer. They can be kept for a very long time if frozen. If left out, the oil in walnuts can turn rancid if not stored correctly.
It’s a considerable amount of work harvesting, hulling, cleaning, and cracking black walnuts, but in the end, when you taste these wonderful treats in your home cooking, it makes it all well worth it.
You can also sell the nuts to Walnut Collector Companies that process the nut meat for retail purposes and shells in various sizes for different abrasive applications including additive to oil drilling muds.