Black Walnut Trees

Facts and Features of the Black Walnut Tree

By George and Becky Lohmiller
September 7, 2018
black-walnut-trees-roots-evil-ascending-the-giants-wikimedia-commons
Photo by Ascending the Giants: Wikimedia Commons

The black walnut tree is one of North America’s most valuable and beautiful native trees, but it does have a “dark side,” too. Here’s what you should know before planting a black walnut in your yard!

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 that inhibits many plants’ growth. 

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.

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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Best time to trim Black Walnut tree?

The Black Walnut tree is encroaching on neighbors property and dropping nuts on parked vehicles. Also causing discoloration on cement driveway that eventually is washed away. Per subject: when is best time to trim Black Walnut tree?

when to prune black walnut trees

The vast majority of foresters will tell you to prune Black Walnut trees in late winter to early spring (February-April). The theory is to prune before the growing season so the wound will cover faster.

However, there are some experts who believe in summer pruning which still starts the wound covering process before fall, resulting in less sap flow, less chance of spreading fungal diseases, less bole sprouting, better working conditions, best time to correct leader problems, and a better view of the crown than pruning in late winter/early spring.

Whatever you decide, NEVER prune when the tree is flushing (leafing out in mid-April to mid-May). And, no matter which season you prefer, it is a good idea to prune your trees. Also, no matter what the season, prune from the top down, not from the bottom up.

Right in the middle, a tree.

I moved into an old house. The yard was a mess. But there were beautiful big evergreens and pines. There had been gardens but they were a mess. Recently I cleaned out the sunny one and found Bee Balm, Bittersweet and Allium. Fine with me. I planted other Prairie Perennials around what I thought was a small Sumac smack dap in the middle of the bed. Was it a squirrel planting? If so they must have planned the location. Anyway, this year I noticed three little green balls, just three mind you. I knew it wasn't a Sumac. Black Walnut or English, I wasn't sure. But, I did some research. Most of what I planted should be fine from the toxin I think. Except of course, as it grows it will block out the sun. This I did not want. I've talked to other gardeners about it. Some really surprised me. They wanted me to cut it down immediately. It's a no good tree! It will kill everything and encourage squirrels. It's MESSY! I'm like, what? You are gardeners, right? And you want to me kill a tree because it might encourage squirrels? What's wrong with squirrels? I like squirrels. So, now I'm stumped (no pun intended) Why is this such a bad thing? And if it's not, then what can I do to keep the sun coming through?

Treed, for Sure!

Hi, Wendy: Thanks for this adventure… er, we mean question! We would just let things evolve and do some selective pruning in the future if necessary. Amazingly enough, in countless places across countless millennia, Mother Nature has managed to find a way for black walnuts, toxins, squirrels, and other organisms, including humans, to peacefully and productively coexist. And did we mention “beautifully”? It sounds like you have a good understanding of and handle on this situation. Peace out! Let the old yard flourish again by its own devices—unless you want to transplant a little sumac from somewhere, that is! Thanks again for the trip… er, the question… and keep up the good work!

Maybe Black Walnut Trees

New home - one year old on an old property with 2 large black walnut trees (I think) & a Rock Elm tree. They don't have nuts which I'm fine with. Last summer we had 6 weeks of no rain so I'm not surprised that there are no nuts this year. Are they really Black Walnut trees or do I have another variety. I've used an app to identify them & they come up as Black Walnut.

Nutty Cycle

Hi, Monica: Black walnuts will often go into a 2-year cycle in which they flower in one year and bear nuts in the next. So stay tuned, and thanks for asking!

Cutting tree NOOO

Relax and enjoy your black walnut. You will reap rewards from it in years to come and what you planted are annuals. Not sure where you live but if you have any winter at all they will die anyway. Another note my most beautiful garden was my shade garden! Plus you get nuts!!

Black Walnut

I have a tree that sprung up after alot of rain. I looked up the long skinny leaves and the closest i found was to a black walnut i dont have a very big yard and live within city limits and while that tree looks beautiful will it cause damage and is that even what i have?

Black Walnut trees

I have 5 old large black walnut trees in my backyard. I answered an ad in a neighborhood paper to sell them . However, I was told yard black walnut trees are not good for furniture because every limb has a knot hole. I don't understand. Can ou explain this to me?

I didn’t know about the knot

I didn’t know about the knot holes, which I am sure there are more than woodland trees, but I do know that neighborhood trees tend to have more nails, chains, spikes, wire etc that will ruin a blade at the sawmill.

Walnut tree growth in southern AZ

Hello I live in Tucson, AZ. I have a large yard and would like to plant a walnut tree. First of all will a walnut survive our long hot summer. I have no problem watering it just concerned about the blistering heat. Second, if the tree will take the heat, what species of walnut would you recommend? South of Tucson there are mass groves of pecan trees, but I would prefer a walnut. Any advice would be greatly appreciated.

walnuts in Arizona

We consulted a few sources and it seems that your walnut options are limited to the Arizona walnut, Juglans major (aka Arizona Black Walnut, Mountain Walnut, New Mexico Walnut, or River Walnut). We have to warn you that some sources say the in the “blistering” heat of the low desert even the native AZ walnuts “barely make it,” no matter how much water you give it (one warned that too much water could rot the roots). Pistachio, almond, and pecan are more commonly recommended.

Walnut tree I think

We have several trees in our yard that look like walnut trees from the pictures on this website. They do not produce nuts but they do produce a green pod in the summer that turns brown in the fall is this actually a walnut tree?

To Tree or Not to Tree

The Editors's picture

Hi, Bert: Thanks for this complicated question that may have a simple answer (or two, or three, or …). First, sometimes it takes as many as 5 or 6 years or more for black walnuts to bear fruit (if this is a recently matured tree). Even then, it might alternate years. Second, black walnut pods (fruit) are usually some shade of green; if yours are turning brown on the tree, they may have some sort of disease or pest, although this is unlikely. Third: Did you look inside a pod? Is there a nut in there? Obviously, no nut, no black walnut tree. So the answer is to have patience, and in the meantime inspect a “pod” or two to try to figure out what you are waiting for, if anything, as this may be some other type of tree. Thanks for asking!

Black Walnut Tree

Our black walnut tree is very productive. Much more than the English Walnut. However, the nut on the black walnut is very small and do not taste nice at all. Is this normal for the small nut? It is almost not even worth collecting, shelling and going through all the process. Can you shed some light in this issue. Thank you

A Hard Nut to Crack

The Editors's picture

Hi, Cassandra: Black walnuts can indeed seem to not be worth the trouble—but they are! It sounds like you’re not curing your nuts. Wash and dry them, then leave in a cool, dry place for 2 to 3 weeks. We think you’ll find them much improved. Thanks for asking!

I have a walnut tree that needs to go.

She is about 40 feet tall and about 15 feet of straight trunk. I live in Columbus Ohio. Cut it down, clear it away, and grind the stump and it's yours.

Walnut tree

Hi Jason,

Is your walnut tree still available? I might be interested in it. My number is 330 447 1780

Black Walnut Tree

We are near Blue Ridge, GA and have a Black Walnut Tree that needs to be removed with care because it is near the house. A large tree maybe three feet diameter trunk. If you are interested please contact me. THANKS,

green leaf defoliation

My walnut tree defoliated all green leaves en masse. I came home from work to find almost every leaf on the ground. I live in Michigan. Anyone else experiencing this? I didn't see sign of disease in the leaves.

Worried about my black walnut tree

We just bought a house in the early summer of this year. There is a huge black walnut tree out back that we just love. I've noticed recently that there is what appears to be moss growing all over it. Is this normal? We really love this tree and don't want to lose it. Please help.

A Mosstery

Hi, Jamie: This really calls for a local arborist, as we don’t know where you are, and even if we did, you don’t say whether “growing all over it” really means what it says, i.e., bark, leaves, everything. And we assume that this is not just lichen growing on the bark. Black walnuts are susceptible to a whole range of pests and diseases, including thousand cankers disease, so it is best to get a professional diagnosis ASAP so that you can begin treatment likewise. Thanks for asking, and good luck!

walnut tree bumper crop

Here in SW Michigan. Our tree has never produced so many walnuts as this season. A friend told us of a conversation he had years ago with an old farmer. He said a heavy drop of walnuts meant a hard, bad winter.
Anybody heard this? Trying to decide how much time to spent in Florida!

This Must Be Nuts

The Editors's picture

Hi, Scott: Thanks for relaying this info. Yes, there is a lot of folklore surrounding what are called “mast” years, when there seems to be an overabundance of nuts and fruit, as though the vegetable world could sense that the animal world was going to need more food during the upcoming winter. Our forecast for your neck of the woods calls for a winter that is not quite so cold as normal but with plenty of precipitation, much of it not in the form of heavy snow. Thanks again!

no nuts this year

I live in Central Michigan. Last year was a heavy production. This year hardly a nut was to be found. If what you heard is true, I'm hoping my tree is the predictor.

Black walnut trees

I love our trees, unfortunately they have contracted the Thousand Cancre Disease , which my arborist says there is no cure for, and that we will lose them all , I have at lest nine in my yard. I live in Colorado.

I hate my tree

My black walnut tree was there when I moved into my house. I'd cut it down but it's too expensive. If anyone wants the wood pm me and you can have for free if you cut it down!

Hate ours too

Hate ours too

Love the wood

Where are you located?

Black walnut

I’m located in Lexington ky 40509 and will travel any distance I have a trucking company so distance isn’t a problem

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