What makes black walnuts different from English walnuts?

Black walnuts have a more robust, earthy flavor compared to the milder taste of English walnuts. They are native to North America, whereas English walnuts originate from Persia. Black walnuts have a thicker, harder shell, making them more challenging to crack. Their trees are also prized for their dark, durable heartwood, unlike the English walnut, which is less valued for timber. Additionally, black walnut trees produce a natural chemical called juglone that can inhibit the growth of other plants nearby.

What is juglone, and how does it affect other plants?

Juglone is a natural toxin produced by black walnut trees, primarily found in their roots, leaves, and husks. It inhibits the growth of certain plants, such as tomatoes, potatoes, and azaleas, by disrupting their respiration processes. This chemical serves as a defense mechanism, reducing competition from surrounding vegetation. Plants sensitive to juglone often wilt or die when grown near black walnut trees. However, some species, like corn and beans, are tolerant and can coexist with black walnuts.

How does tree spacing affect black walnut growth?

Proper spacing is crucial for the healthy growth of black walnut trees. Trees planted too closely compete for sunlight, water, and nutrients, leading to stunted growth. Ideal spacing ranges from 25-30 feet between trees to allow for full canopy expansion. For timber production, tighter spacing can encourage vertical growth, producing straighter trunks. However, overcrowding should be avoided as it reduces nut production and increases the risk of disease.

How long does it take for a black walnut tree to produce nuts?

A black walnut tree (Juglans nigra) typically begins producing nuts between 10 to 15 years after planting, though optimal nut production may take 20 to 30 years depending on growing conditions, soil quality, and tree genetics. Some trees may start bearing a small number of nuts as early as 6 to 8 years under ideal conditions, such as well-drained, fertile soil and full sunlight. For example, a well-managed black walnut orchard in Missouri or Indiana, where conditions are favorable, may see early nut production around year 8, while a naturally growing tree in a forest setting might take closer to 15 years before producing a reliable crop. Peak nut yields generally occur when the tree reaches 30 to 50 years of age, making black walnut cultivation a long-term investment.

How do you husk black walnuts?

Husking black walnuts (Juglans nigra) involves removing their thick, green outer husks to access the hard inner shell. The husks can be softened by allowing the nuts to sit for a few days after falling or by rolling them underfoot or driving over them on a hard surface. A simple method is to wear gloves (to prevent staining from the husk’s dark juices) and use a hammer, rubber mallet, or a sturdy knife to peel away the husk. Another efficient approach is using a corn sheller or a black walnut dehuller, which speeds up the process, especially for large quantities. Once husked, the nuts should be rinsed thoroughly in water to remove any residual husk material and then spread out to dry for a few weeks before cracking. For example, in rural Missouri and Indiana, where black walnuts are commonly harvested, many people use a modified cement mixer or wire mesh drums to remove husks efficiently in bulk.

How do you collect black walnuts?

Collecting black walnuts (Juglans nigra) involves gathering the nuts as they fall from the tree, usually in early to mid-autumn (September to October) when the husks turn from green to yellowish-brown or black. The best method is to walk the area beneath the tree daily and pick up freshly fallen nuts before they start to rot or attract pests. For large-scale collection, tools like a nut roller, wire basket picker, or even a tarp spread under the tree can make the process more efficient. In commercial operations or farms, mechanical nut harvesters, similar to those used for pecans, can be used to speed up collection. For example, in Missouri and Ohio, where black walnuts are harvested commercially, farmers often use rolling nut harvesters to gather large quantities quickly. Once collected, the nuts should be hulled, washed, and cured before cracking for consumption or sale.

Learn How to Collect, Husk, Stratify, Plant, and Grow Black Walnut Trees

This comprehensive guide will teach you everything you need to know about growing your own black walnut trees.

Collecting Nuts

There are three methods to collect walnuts: picking them up from the ground in the fall, shaking them loose with a telescopic branch holder, or manually shaking individual branches. The easiest and safest method is to gather walnuts after they fall to the ground in the autumn. A mature tree can yield over a thousand walnuts during the season.

Removing the Husk

Husk removal can be a messy and time-intensive task. There are two common methods:

Soaking in a Pail: Place approximately 50 husked walnuts into a five-gallon pail filled with water and soak for two days. This softens the husks, making them easy to remove by hand.
Using a Drum and Agitator: Fill a 20-gallon drum halfway with water and add about 200 walnuts. Let the walnuts soak for 48 hours. Then, use a power drill with an agitator attachment (commonly used for mixing paint or plaster) to stir the water for 5 minutes. Scoop out the mixture with a small bucket and pour it into an upturned milk crate placed on another milk crate to create a sieve. Spray the nuts vigorously with a garden hose to separate the husks. Store the cleaned nuts in a cool, moist location unless you intend to crack them for consumption.

Video Tutorial

Watch a step-by-step video on processing walnuts, including picking, husking, stratifying, and planting, to guide you through the entire process.

Stratification

Black walnut trees are temperate species that require stratification to germinate in the spring. Stratification is the process of artificially inducing dormancy for a specific period to promote germination. Black walnuts need 3 to 4 months of dormancy before they can be sown.

To begin, clean the nuts thoroughly and soak them in water for 24 hours. After soaking, strain the nuts and place them on a towel to dry at room temperature for about 10 minutes. Prepare several large, self-sealing plastic bags by filling them with a mixture of nuts, peat, and potting soil, leaving a small amount of space at the top. Seal the bags and gently shake them to ensure the nuts and soil are evenly mixed. Be cautious not to overcrowd the nuts, as insufficient spacing can cause them to rot within weeks.

Place the filled bags flat, one on top of another, in a second refrigerator—preferably one kept in the garage or purchased secondhand for this purpose. Avoid using a fridge where food is stored to maintain hygiene. After several months, the nuts will be ready to plant. For example, if you begin stratification in December, the nuts will typically be ready for planting by spring.

Planting Black Walnut Trees

To begin planting black walnut trees, remove the stratification bags from the refrigerator and bring them to your planting site. For a traditional planting approach, use a string line secured between two stakes as a guide to plant seeds in a straight row. Dig small holes approximately 5 inches deep, spaced 15 to 20 feet apart along the line, using a shovel. Place one seed in each hole and cover it with soil. To create rows of trees, repeat the string-line method, ensuring rows are spaced 25 feet apart.

Transplanting Black Walnut Tree Seedlings

When transplanting black walnut seedlings, prepare deep, round holes in the soil using an auger. Ensure the holes are wider and deeper than the roots of the seedlings. Depending on the number of seedlings, you can use a handheld or PTO-driven auger. The string-line method can also help align and properly space rows of transplanted seedlings for optimal growth.

Pruning Black Walnut Trees

For nut production, there are two primary pruning methods: heading and non-heading. Heading involves trimming the main trunk to a specified height each season to encourage branching, potentially increasing nut yield. Non-heading, on the other hand, focuses solely on pruning lateral branches.

If growing black walnut trees for timber, lateral branch pruning is essential to ensure the development of knot-free wood suitable for veneer and lumber. Begin pruning in the second year after transplanting to allow the tree time to establish itself. Continue annual pruning until the trunk reaches a sawlog length of 12 feet. Ongoing pruning beyond this point can increase the sawlog length, significantly enhancing the tree's value.

Black Walnut North American Growing Zones

Black walnut trees are native to Eastern Canada and the United States, with the highest concentrations found in the Southern States. While originating in Eastern North America, black walnut also thrives in favorable microclimates around the globe.

Growing Black Walnut for Wood and Timber

High-density tree stands promote the growth of darker-colored heartwood, which significantly increases the wood's value. Dense planting also encourages faster and straighter tree growth. Seedlings can be thinned once they reach an 8 to 10-inch caliper, allowing the remaining trees more space to grow larger and healthier.

Black Walnut Wood

The heartwood of black walnut ranks among the most durable woods, comparable to cedar, chestnut, and black locust, even in conditions conducive to decay. Its unique color and grain make it a prized material for furniture, cabinetry, millwork, flooring, and decorative interior applications. Black walnut is also a preferred wood for gunstocks due to its low movement after seasoning. Figured walnut stocks are highly valued for high-end shotguns, sporting rifles, bowls, and artistic carvings.

Black walnut wood is commonly used to craft bookcases, desks, dining room tables, bedroom sets, office furniture, and many other high-quality pieces. Its durability and aesthetic appeal make it a top choice for both functional and artistic applications.

Tree Spacing Calculator for Walnut Trees

The following comments were collected from a national wood products discussion forum using black walnut wood in the United States.

Comment from contributor A:

Recognized as one of the most lovely and finest hardwoods, these days black walnut wood is in short supply. As a result, the wood is often cut into veneers and used to cover less-expensive woods in furniture making. A large diameter tree with a tall straight trunk can be worth tens of thousands of dollars and can produce enough veneer to cover 3 acres. And yes, there are black walnut tree rustlers – just ask mu neighbor.

Comment from contributor B:

The big money comes from veneer grade black walnut trees.They will be in the saw log class at 14 inches in diameter. Veneer grade trees will be 21 inches in diameter. The price per log triples from saw log to veneer. Get in touch with your service forester or private forestry consultant. Anyone with tall veneer grade trees may have a gold mine that is worth investigating further.

Comment from contributor C:

If you have one or two or even a dozen black walnut trees in your yard and think you are sitting on a fortune in valuable wood, think again. The most valuable trees are straight and tall with even grain and diameter over 16 inches at breast height. Yard trees rarely have these characteristics. In addition, many yard trees have had nails, fence wire, horseshoes, and other metal objects attached that grow into the wood. This ruins the most valuable part of the tree from a veneer perspective and drastically reduces its value for sawlogs. Very rarely will a timber buyer mess around with yard trees.

Comment from contributor D:

If your black walnut tree has a damaged or crooked trunk and you want to get a nice straight tree that is much more valuable later on, you can cut down smaller trees with an established root system to the ground and they will send up a shoot that grows straighter and faster than the original.

Comment from contributor E:

Several key characteristics determine the value of this tree for timber or veneer; trunk diameter, merchantable height, and how free the trunk is from defects such as knots and damage from lightning. Quality lumber and veneer trees generally have diameters of 18 inches or greater.

Comment from contributor F:

The length of tree trunk that can be used for lumber or veneer is called its merchantable height. Merchantable height is usually the trunk height a foot off the ground to start of major branches or forking. Minimum merchantable height for lumber and veneer black walnut trees is 10 feet. Quality lumber and veneer trees will have merchantable heights that are several times that height. The quality of a hardwood tree is measured by how free its trunk is from defects such as crookedness, limbs, knots, scars, swellings, bumps, cracks, holes, insect or disease damage, and wounds. Other factors being equal, the fewer the defects, the more valuable the tree. High-value lumber and veneer trees have few visible defects. On the other hand, Walnut trees with numerous defects are of little economic value. In general, the larger the tree's diameter and merchantable height and the more free the trunk is from defects, the greater its economic value for lumber or veneer.

Comment from contributor G:

With all these positive attributes black walnut still accounts for less than 1% of the hardwood production in the US. Walnut wood is expensive, generally the highest priced domestic hardwood. Most logs are short; special grading rules allow for 6’ being included in FAS, the top grade. Lengthier logs would be worth considerably more.

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