Black Walnut Trees

Facts and Features of the Infamous Black Walnut Tree

By George and Becky Lohmiller
January 23, 2020
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Photo by Ascending the Giants: Wikimedia Commons

The black walnut tree (Juglans nigra) is one of North America’s most valuable and beautiful native trees, but it does have a “dark side.”  Here’s what you should know before planting a black walnut in your yard—and all about harvesting and eating walnuts, too.

A Few Black Walnut Tree Facts

  • The easily worked, close-grained wood of the black walnut has long been prized by furniture- and cabinetmakers for its attractive color and exceptional durability. Its logs are in such demand for veneer that “walnut rustlers” have made off with trees in the dead of night and even used helicopters in their operations. 

  • The early settlers discovered black walnuts growing in mixed forests from Canada to northern Florida and west to the Great Plains. They found that its rich-brown heartwood was exceptionally resistant to decay and put it to use as fence posts, poles, shingles, and sills.

  • When surrounded by other trees in the forest, black walnuts grow straight and tall with few, if any, lower branches.

  • When planted in the open, the tree will branch out closer to the ground, developing a spreading shape that makes it easier to harvest its sweet, round, two- to three-inch nuts.

  • Settlers snacked on the nutritious walnuts out of hand, added them to soups and stews, and ground them into meal for baking; the hard shells provided a perfect package for storing the nuts over winter.

Black walnut tree

The “Dark Side” of Black Walnuts

Although the black walnut has many uses and benefits, the tree does come with a caveat: The black walnut’s roots, which may extend 50 feet or more from the trunk, exude a natural herbicide known as juglone in its roots, leaves and fruit husks.

This chemical inhibits many plants’ growth under and around the tree, thereby limiting the tree’s competition, leaving more water and nutrients for itself. 

Tomatoes, potatoes, apples, pears, berries, and some landscape plants such as rhododendrons, azaleas, and lilacs may be killed or stunted if grown in close proximity to black walnut roots.

A Great Shade Tree

In spite of this, black walnuts make great shade trees for larger properties. They commonly grow to 50 feet or taller and about as wide, and specimens of more than 100 feet have been recorded.

Black walnut’s large, fernlike foliage provides light, airy shade for those grasses and ground covers not affected by juglone. In autumn, the leaves turn bright yellow, contrasting nicely with the tree’s rugged, dark bark.

Black walnuts require a deep, fertile soil with a near-neutral or slightly acidic pH. They are pretty much disease-free and are threatened by few pests, with the exception of perhaps an occasional helicopter.

Picking Up the Nuts

Thud! Thud! Most walnut tree owners have a love/hate relationship because of the fruit which the tree drops in late summer though October. The size of a baseball and colored lime green, the fruit is quite heavy. It makes quite a mess and can be viewed as a nuisance.

Walnut tree owners will spend hours picking up the fruit some years. If you don’t remove the nuts, you’ll trip over them in the dark for the rest of the year (while they rot and mold on your lawn). Hire the kid down the street to pick up those nuts *but be careful not to overpay per nut or you’ll go broke)! 

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Photo Credit: John A. Anderson

Harvesting and Eating Black Walnuts

If you’re willing to do the work of cracking the outer shell, the “meat” inside is edible, as the squirrels will attest; squirrels have little problem chewing through the shells. (Note: Black Walnuts are different than the English Walnuts more commonly sold in stores and shown at right above.) 

The sweet, earthy nutmeat inside is well worth the effort. Your grandparents may have harvested the walnuts which can be eaten raw or added to baking (cookies and bars). They can also be toppings on ice cream and cakes, enjoyed as a sweetened candy nut, or ground into meal for a unique flour. 

To harvest, collect the nuts as soon as possible to avoid mold and remove the husks immediately. Wear gloves as the husks stain your hands (and anything they touch). If the nut is too hard, wait a few days and it will brown and soften up.) To remove the husk, you can simply step on them gently with an old pair of shoes. Hose down the nuts in a large bucket to remove any remaining husk.

Dry the walnuts for a couple of weeks on a screen or drying rack or in a hanging mesh bag. You can store them unshelled up to a year. Crack the shell with a hammer to get to the nut meat. (Strike at a 90-degree angle to the seam until the nut cracks). Use pliers to easily clip away the shell to release the nutmeat. Allow the freshly removed nutmeat to dry for a day before storing.

Do you have a black walnut tree? Please share your comments, questions, and advice!

Source: 

This article was originally published in March, 2008 and has been updated.

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Reader Comments

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Yes, deer will eat them, I

Yes, deer will eat them, I think it is candy for deer. lol I keep mine fenced until they are about 4-5' tall and the you still need to protect the trunk from deer rubs.

I have or I think I have

I have or I think I have black wallnut trees on my prop. about 35 feet apart. For 15 years I,ve lost many pine trees that I've planted around these black wallnut trees. Is there a pine tree that resists the JUGLONE that was talked about?

I take exception to your

I take exception to your comment regarding Black Walnut pest.
You mention few are out there, we have 17 walnut trees in our back yard.
We live in S.W. Ohio 2.7 miles from a large Veneering company. They are suspect of importing diseased walnut trees from Colorado. We have a major infestation of Walnut Twig Beetles (size of a sesame seed) which carry a fungus which causes 1000 Canker Disease.
Our situation is so bad the state of Ohio Agriculture Dept. has conducted training classes in our yard. We've had Professors from Ohio State University and University of Tennessee investigating and taking samples. Plus the Ohio Division of Forestry Department had 25 of their personal here for observation.
We currently have one of in excess 110 traps around the county. These traps are not to catch the beetles for disposal rather they are for verification of the infestation in other areas.
It's now up to us to take down these dead or dying trees. Then we must figure out a means of disposal without removing any portion including saw dust from the county of which we live Butler County Ohio.
I decided to pass this information on in the event your Walnut trees decided to start dropping leaves early and often all summer long including.

Thanks for your comment. This

The Editors's picture

Thanks for your comment. This column was written in late 2005 or early 2006 and we appreciate your update.
The walnut twig beetle is a pest that seems to be increasing among black walnut trees (primarily affects black walnut Juglans nigra). Tinier than a grain of rice these beetles carry the fungus Geosmitha morbida that eventually (within a couple or few years) infects the tree and starves it to death. See: http://www.aces.edu/ucf/Blackw...
Disposal of the remains can be a complicated and costly procedure.

Do you need to fertilize the

Do you need to fertilize the soil and also what pesticide do you need to treat the black walnut trees? Thanks

It would probably depend on

The Editors's picture

It would probably depend on whether the black walnuts grow naturally in your area. If they do, we'd say you needn't bother fertilizing, unless you are setting up a stand of trees to harvest the nuts or wood, or if the tree begins to look unhealthy. When fertilizing, we'd recommend that you test your soil for nutrients and then contact your county's Cooperative Extension or an arborist to see what fertilizer is needed for your local soil, for black walnuts, and for the age of the tree. Soil pH is best around 6.2 to 7.2.
 
The same would apply to pesticides. If the tree is native to your area, and you are just interested in the tree as a landscape feature, then it would not need pesticides unless a specific problem arises. If, however, you are planning to harvest, then monitoring for specific pests, such as the walnut husk fly, would be called for, with the appropriate pesticide that is safe for edibles if harvesting the nuts rather than the wood (check with an arborist or your local garden center for what's appropriate in your area).
 
For more information, you might be interested in the following:
 
http://www.walnutcouncil.org/r...
 
http://extension.usu.edu/files...
 
http://web.extension.illinois....
 
http://www.walnutcouncil.org/r...

I live in a neighborhood that

I live in a neighborhood that has many mature trees and I have mulitple black walnuts on my property. They are mature but I do not harvest them. The past few years I have been losing many large and small branch's some in storms but most are brought down by the slightest wind gusts. Is this normal? Is there something I can do to prevent it?

This can happen when there is

The Editors's picture

This can happen when there is too much weight on the ends of the branches. Just prune to thin your trees. Be careful not to overprune or strip the tree on one side or this can cause the tree to get weakened and the branches to bend and break, too.

I bought a large farm 2 years

I bought a large farm 2 years ago (2011) and dicovered about 8 fully grown walnut trees on the edge of the fields in the woods. I am going to try a harvest this year for pesonal consumption. It is august now and was wondering what a good time to and how do I know the best time for harvest. I am in Maryland.

Black walnuts are harvested

The Editors's picture

Black walnuts are harvested in the fall (mid to late September) once the hull changes from a solid green to a yellowish color and is soft enough that you can dent it with your thumb. The walnuts should ripen on the tree, so you can shake the tree or just wait until the nuts fall. Here is a good reference page on how to harvest and prepare the walnuts:
http://www.extension.umn.edu/yardandgarden/ygbriefs/h404blkwal.html

My neighbor has a huge Black

My neighbor has a huge Black Walnut on the border between our properties. It is exactly where it does us the least good, because it is overshadowing an area that would be perfect for a garden. I call it the "Black Widow Tree".

We have a very old very large

We have a very old very large black walnut. It is a lovely tree but drops yellow spotted leaves all summer. Keeps lawn covered and messy.

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