If you live in Missouri, you’ve likely seen black walnut trees frequently and may even have one in your yard, but have you ever tried processing black walnuts to eat?
The Missouri Botanical Garden’s Center for Home Gardening shared the following information on black walnuts, and step-by-step guide to harvesting and preparing black walnuts to eat.
About black walnuts
Maple, Acer miyabei ‘Morton’ STATE STREET. Photo by Tom Incrocci.
Black walnut (Juglans nigra)is a large, deciduous tree native to much of the eastern United States including Missouri. They produce high quality timber and delicious nuts that humans and wildlife alike love.
Black walnuts are also known for their allelopathy, or ability to hinder the growth of nearby plants using biochemicals. Other plants with allelopathy include sunflowers (Helianthus annuus) and common milkweed (Asclepias syriaca). The main allelopathic compound in black walnuts is juglone. Buds, leaves, roots, and nut hulls produce the highest concentration of juglone. Some plants are more sensitive to juglone than others.
Ericaceous plants (such as azaleas, rhododendrons, and blueberries) and solanaceous crops (such as tomatoes, peppers, and potatoes) are a few of the most sensitive. Don’t plant these under a black walnut or use the leaves or hulls as mulch around these plants. Some plants that are tolerant of black walnut include grasses, sumacs, viburnums, ferns, and hellebores.
Where do Black Walnuts Grow?
Black walnuts grow best in deep, rich, well-draining soils, but are adaptable to a wide range of growing conditions including clay soils and the occasional drought. If you want to add a black walnut to your home landscape, be sure to keep their ultimate size in mind. These are large trees capable of reaching 75-100 feet tall with a similarly large, spreading canopy. They are great choices for large yards or parks, but you should not plant them close to a house or other structure.
Did you know Missouri grows twice as many black walnuts as any other state? Black walnut is Missouri’s state nut. Missouri is considered the black walnut capital of the world.
Missouri grows twice as many black walnut trees as any other state, and is rightly considered the black walnut capital of the world. In fact, black walnut is the official state tree nut of Missouri.
Threats facing black walnuts
Black walnuts in Missouri are under threat from a disease called thousand cankers disease (TCD) that is spread by the walnut twig beetle. Symptoms include flagging, canopy dieback, and tiny beetle exit holes in the bark. Although it hasn’t been detected in Missouri yet, this disease has the potential to devastate the ecologically and economically significant population of black walnuts in the state. How can you help? Never move firewood more than 50 miles from where it was harvested and if you see a black walnut tree with symptoms of TCD, report it to the Missouri Department of Conservation. For more information on TCD, including how to report a potentially sick tree, check out this page from the Missouri Department of Conservation.
Black walnut uses in food
Commercially processed and packaged black walnut nutmeats can be found at grocery stores around the state in the fall alongside their English walnut (Juglans regia) cousins. The flavor of black walnuts is richer and deeper than English walnuts, with earthy, floral, and even fruity notes. Black walnuts are excellent in baked goods and confections of all sorts. Black walnut ice cream is one of my favorite seasonal treats.
Harvesting Your own black walnuts
You can harvest and process your own black walnuts by following a few simple steps and using the right tools. There are other methods besides the one described here, and even nut cracking machines specifically designed to make easy work of the tough black walnut shell. If you intend to make a yearly tradition out of harvesting and processing your own black walnuts, it might be worth it to invest in a specialty nut cracker.
Step 1: Gather the walnuts
Fallen walnuts can be picked up by hand or using a rolling nut harvester tool. Some folks try to avoid walnuts that are completely blackened, and only harvest ones that have mostly green or yellow hulls. But the darker the hull, the easier it is to remove, and in my experience, using mostly blackened walnuts did not negatively affect the flavor.
Step 2: Remove the hulls.
The nuts are contained inside a fibrous hull that must be removed first. This hull contains tannins that will stain your clothes and skin, so be sure to wear thick, rubber gloves and clothes you don’t mind getting stained. Stomp on the nuts or cut into the hulls and remove as much of the outer hull as possible. There will be a layer of dark, sticky residue left behind that will be removed in the next step. You might come across some small worms in the decomposing hull. These are the harmless larvae of the walnut husk fly. They do not damage the shell or meat and the nuts are still perfectly good to eat.
Step 3: Remove the residue.
Place the nuts in a bucket and fill with enough water to fully cover. Vigorously swirl the nuts and change out the water several times to clean off as much of the residue as possible. I used an old broom handle but any sturdy stick will work. Discard any nuts that float.
Step 4: Curing
Put the cleaned nuts on a screen or in a mesh bag and allow them to fully dry and cure for 3-6 weeks out of direct sunlight. Make sure where you store the nuts is squirrel proof. Once they are fully cured, the whole nuts can be stored in a cool, dry place for up to a year.
Step 5: Cracking
Black walnut shells are incredibly hard, much harder than English walnut shells. I certainly have more respect for the strength of squirrel teeth after this experience! You will need a hammer, a pair of diagonal cutting pliers, and a hard, sturdy surface. Make sure the nut is stable and then crack them open with the hammer. Avoid smashing the nuts to smithereens, as this will make it harder to harvest the nutmeats.
Step 6: Removing the nutmeats
Once you have halved or quartered chunks of walnut, use the diagonal cutting pliers to snip away pieces of shell until you can free the pieces of nutmeat.
Step 7: Enjoy!
You an eat black walnuts right away or store them in the refrigerator for a short time. For longer term storage, store the nutmeats in the freezer.
Justine Kandra
Horticulturist
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