Everything There Is To Know About Black Walnut

Both European walnut and American black walnut share similar levels of strength and density, and are great choices for furniture, flooring, cabinetry and kitchenware.[image]

American Black Walnut Wood

• Black walnut, or American black walnut (juglans nigra) is native to Eastern and Central North America, but they happily grow in a wide variety of climates.

• There are over 20 species of walnut trees that all produce nuts, but black walnut is amongst the most abundant species in North America. It's also the most desired for its wood and nuts.

• Usually used to make higher-end furniture and other household items due to the comparatively higher material cost, strength, colour, patterns and smoothness of this wood.

• Black walnut is a much darker colour than European walnut, and it also tends to grow a little taller and straighter than its European cousin, adding to the desirability.

European Walnut Wood

• Often referred to as Persian walnut, English walnut, European walnut - or just walnut - the second-most-popular species [juglans regia] actually originated far more east than England, in Asia.

• This species was reportedly brought to Europe by the Romans, who revered it first and foremost for the sweet, nutritious walnuts, and used the wood for smaller, more ornate pieces.

• Thankfully, the now-European walnut tree adapted well to the new climate and continues to grow across much of Europe, Asia and the UK.

• While European walnut doesn't grow as tall or have as distinctive colouration as American black walnut, it often will have more interesting growth patterns such as burls, crotches, curls and knots.

Both European and black walnut are ideal for a wide variety of uses both indoors and outdoors. Some of the most common use-cases for walnut wood are:

• Furniture such as desks, tables, chairs, dressers and shelves.
• Kitchen cabinets, cutting boards, salad bowls, spoons & other kitchenware
• Clocks & accent decor pieces.
• Solid wood flooring
• String and wind instruments such as violins, guitars & flutes.
• Chess and checkerboards - usually used in contrast with a lighter shade wood such as ash or beech

Despite the slightly higher price of black walnut when compared with other popular types of wood, the benefits of this wood are usually well worth it to woodworkers and home-owners alike.

Woodworkers love the quality, stability and work-ability of walnut wood, meaning that they can be creative with their designs and enjoy the process of crafting the wood even more.

For anyone who chooses to purchase some black walnut wood pieces for their home, they will also appreciate the quality, strength and stability of this wood, and needless to say - the beautiful patterns and colouration. 

The colour of a particular piece of black walnut will vary depending on the age of the tree, which part of the tree it comes from, and also the conditions that the tree was grown in.

In the Sapwood (outermost part), the wood ranges from a honey-yellow to grey to a bright white. This is the newest growth of the tree and so it is typically much lighter in colour than the heartwood.

The Heartwood (inner most part) is where walnut wood really gets its famed rich colouration. Here, it ranges from deep chocolate-brown to a purple-grey, sometimes with hints of red or darker stripes throughout.

Maintaining Wood’s Vibrancy

The trick maintaining the quality and colour vibrance of black walnut, (or any wood, really), is to re-oil it over time. Of course, how often you do this will depend on the sort of use-cases that the wood is in; for example a back walnut plate or cutting board would need to be oiled more regularly than a black walnut vase.

What's interesting about black walnut is that it gradually gets lighter with age - adding oil will help to keep the wood darker. This is in contrast to other familiar hardwood species like cherry, which naturally gets darker with age. If you ask me, the fact that walnut gets lighter with age is convenient, as it balances out the natural darkening that will happen over time from applying layers of oil.

Generally, all species of walnut have fine grain. This produces wood that can be easily made into straight boards for craftspeople, carpenters and cabinet makers to then work their magic with. Sometimes there can be irregularities such as burls or knots in walnut wood.

A burl is caused by what is essentially an ‘abnormal’ growth pattern in the grain that naturally occurs as a result of the walnut tree’s ability to rapidly regrow new branches.

Burls and knots in walnut wood produce very interesting and beautiful patterns, they’re even part of what makes walnut wood so popular, but usually burled walnut wood is used for smaller items as the grain around a burl is not suited for larger pieces of furniture.

Walnut wood a strong reliable wood and can take quite a lot of pressure, but it's still relatively lightweight. This is why it's commonly used for cutting boards, large furniture pieces and flooring.

The fine grain means the wood is very dense and so it absorbs shock well. Black walnut scores 1010 on the Janka Test, which is not quite as high as acacia, but anything of 1000 or over is considered wonderful for flooring.

What’s the Janka Test, You Ask?

The Janka Test is a universal test to be able to measure the hardness of a particular wood. It's done by measuring the pressure needed to press a solid steel ball with an exact diameter of 11.28mm (0.444'') precisely half way into the wood (ie: so that half of the ball is in the wood, and half is sticking out).

Growing these trees for fun, shade, wood and walnuts can be a very pleasant and easy process, but there are a few things to know before you go and plant one, or several of them..!

Something to Note Before Growing Walnut Trees

• When it comes to planting a walnut tree in your garden, it's important to be aware that the roots of the black walnut produce a natural herbicide called 5-hydroxy-1,4-naphthalenedione - or the more commonly-known name of Juglone.

• It is sometimes used in herbicides, and due to the natural red-orange pigmentation, Juglone is used as a pigment in inks or dye for clothing, hair, cosmetics, and even food.

• Juglone exists in all species of the walnut family but is present in the highest dosage in black walnut. It gets deposited into the soil around the tree via the roots, but is actually in the highest amounts in the newer, fastest-growing leaves.

As mentioned, this chemical is a natural herbicide which quashes or even kills many species of plants and trees that try to grow within a few-meters-radius of the tree. [image]

Something Else You Should Know:

Seeing as some black walnut roots can spread 50 feet or more from the base of the trunk, you may want to consider where you choose to plant a black walnut tree (if at all) in your garden.

Juglone is also known to be unsafe for horses and dogs to ingest, we'll cover more on assessing the risk of black walnut concerning the safety of some species of animals such as dogs and horses a little further down in this guide.

Despite the fact that juglone will cause issues for the nearby growth of some species of plants, black walnut trees in the garden make great shade-providers, growing outwards almost as much as they do upwards.

One benefit of juglone is that it makes the black walnut an essentially disease-free tree that very few pests will go near. The foliage of the black walnut are a little similar in appearance to ferns, and will turn vibrant golden-yellow during the autumn.

This makes for a striking contrast up against the dark and rugged bark of the tree. For optimal growth conditions, the best soil to grow black walnut in is deep and fertile with a near-neutral to ever so slightly acidic ph..[image]

While the majority of walnuts that are eaten today are from the European walnut tree, the nuts from the black walnut are also edible, and delicious. The walnut fruit will begin to appear in early spring and drop off the trees throughout late summer to October.

If you are harvesting the nuts to be eaten, be sure to collect them as soon as possible after they fall to stop mold developing. As you can imagine, the ground covered in messy fruit the size of apples can start to get pretty old pretty quickly, depending on where the tree is planted and whether or not you have a use for the walnuts.

Squirrels will also be attracted to the walnuts and have no issues with getting through the tough shell, or the presence of juglone. Make sure to wear gloves when handing the fruit and outer shell as it will stain your hands, clothes, shoes...everything!

Why Grow Black Walnut?

Walnut wood (particularly black walnut) has demanded premium prices since the early 1700s, that's decades before the Boston Tea Party, or 150 years before the California Gold Rush began.

Today an acre of mature black walnut trees is has an approximate value of over $100k in timber alone - it's extremely understandable why black walnut farming is a desirable occupation with such a highly sought after, diverse and sustainable crop.

Black walnut is farmed all across North America, but the majority of it comes is grown in the eastern-half of the U.S. While the crop might take a couple of decades to start producing high volumes of wood and walnuts, a fully matured walnut orchard is quite the asset to own.

This is due to the high value of both the black walnut wood, and the walnuts. Very often, walnut farmers will also take advantage of the wide spaces between each tree and grow additional crops (that are immune to juglone) while the trees are still smaller.

Walnut tree farmers usually grow walnut for both the nut and the wood, as both are highly prized (and priced) renewable resources.

How It’s Grown:

1. Farmers will often prune the lower branches of the trees, which encourages faster growth and helps to cultivate straighter, more uniform trunks (making for a more desirable piece of wood to work with).
2. The branches that are pruned are not wasted but also are used for their wood and often contain a good portion of the tree’s walnuts.
3. As they are trimmed, it encourages the tree to put more energy into the main trunk while also encouraging it to continue growing new branches with, you guessed it - more walnuts!
4. This process means that during the 30 or so year cycle of the trees’ growth for timber, it can be simultaneously producing a steady crop of walnuts as well as smaller pieces of timber.

”Greener” Farming Practices for Black Walnut

Thankfully, this means that walnut farming is a relatively diverse form of farming where an effort is made to waste less.

The farmers have a direct incentive to follow these practices due to the high market value of what they produce and being able to maximise the full potential of their crop.

When it’s harvested, seasoned and dried there is very little shrinkage from the water evaporating, compared with many other woods of its caliber.

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Black walnut wood will only pose adverse affects or be potentially toxic to a human if you actually sat down munched on it or ingested/inhaled a big spoon full of walnut wood dust.

Furthermore, for most people, the adverse reaction to such a scenario would be more of a mild irritation to the eyes, itchy skin or stuffy sinus... and injecting any kind of dust will cause that to happen.

In most cases, walnut wood, and particularly black walnut wood is too hard to actually cut into with a kitchen knife. As mentioned, it's also usually sealed with a natural mineral (food-safe) oil and is why walnut is commonly used for boards, bowls and other kitchen utensils. 

If you are allergic to walnuts, other nuts, or if you are at all concerned, it's best to double-check with your doctor, but black walnut wood itself should not pose any sort of threat or reaction.

Please do not take this as direct medical advice as I am not a doctor, if you are concerned about having a reaction, check with your local doctor or GP. The levels of juglone (natural herbicide) dramatically decrease after the tree is no longer growing or alive, thus the wood itself will contain negligible amounts of juglone.

Absolutely! There are very good reasons why black walnut is so often used for cutting boards, bowls, plates, spoons, and all manners of kitchenware.

But, be careful that you try keep walnut wood out of any dog's reach if they tend to chew furniture as their strong jaws can crack the wood. If a dog ingests pieces of the wood, it could potentially cause a bad reaction and result in a very sick puppy, the same goes for horses.

If you're concerned that an animal may be experiencing a reaction to juglone or black walnut, please make sure to contact your local vet immediately. Again, if you do have any doubts or concerns due to a nut allergy it's always best to consult a medical specialist for advice about your specific situation.