Black Walnut Trees

Facts About the Infamous Black Walnut Tree

By George and Becky Lohmiller
August 19, 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 how to harvest and eat the tasty walnuts, too!

Facts About the Black Walnut Tree

  • 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. This substance is also found in the tree’s leaves and fruit husks.

Juglone does serve a purpose, though. It 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 or within the tree’s drip line (i.e., under the tree’s canopy). Plan your landscaping accordingly!

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, but 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.

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 the dropped walnuts (just be careful not to pay per nut—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 in the photo 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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Black walnut fruit rot

If the walnut fruit husk has begun to rot on the ground is it too late to harvest? Basically, can you just let the walnut husk rot away and still keep the nut or will it rot too?

Walnut Husks

The Editors's picture

It really depends on how far gone the husk is. If the husk is completely rotted, we wouldn’t recommend keeping that nut, as the nut will have been left exposed to fungi and pests that could have penetrated the shell. However, if the husk looks like it’s only just started to break apart, you can get away with collecting the nut. 

Black walnut cleaning

I use a small cement mixer,run for about 20 min for each batch of 5 gallon, wtth water

Black walnut

If you don't clear the fruit from your yard, or if you leave a small pile in a corner, you will be "blessed" with a completely bare patch of soil for a year. Ask me how I know.... The last time the wind blows as many walnuts seem to fall as have fallen all summer and fall together.

Black walnut trees

Are there people that buy very old black walnut trees? I have 3 very old trees in my yard and was thinking of getting rid of some.

Colic in horses

I have also been told that black walnuts are toxic to horses and can cause severe colic. Black walnuts should never be on a property where horses are kept.

Black walnut trees and horses

The Editors's picture

Yes, indeed. There is a similar comment lower on this page. Horses are generally only affected by shavings made from the tree. Do NOT use in bedding. 

Squirrels

I have a black walnut tree in my backyard. Its super beautiful and provides a nice shady cover for the hot Mid-Atlantic summers. The biggest problems is that it attracts squirrels (aka tree demons). They not only steal all my tomatoes, dig holes everywhere, but they also have been chewing my outdoor lights and stealing the bulbs. They are cute buggers but what I pain - I never knew they were such a nuisance.

Giant Black Walnut trees

I have read that before contemporary road paving, that many early 1800s rods were paved with black walnut slats. The wood was plentiful, inexpensive, tends to resist rot and last longer in the damp earth than other wood. It was an effective way to maintain roads in mud seasons. In earlier times there were giant black walnut trees, 30' in circumference and more than 200' tall. These were all cut to pave roads.

Black Walnut Tree

I let the squirrels have them. I honestly didn't know they were edible for humans. My tree is right by my driveway which makes a pretty big mess.

Black Walnuts

I love in south Louisiana and remember as a younger adult always having a few trees. Well, time has passed and the trees are gone. I with I could find someone that would be willing to send me some.

Black walnut tree

Wonderful tree but I am told it can cause colic in horses? Is this accurate?

Black walnut toxicity

The Editors's picture

Black walnut trees are odd in that they are safe for all livestock except horses, and horses are generally only affected by shavings made from the tree. Do NOT use in bedding. Black walnut trees are, however, toxic to some species of plants if growing within a certain range of the tree. In fewer instances, shedding pollen can cause allergic reactions in horses and people as well as kidney effects in animals that ingest hulls.  Black walnuts do not pose any threat of toxicity to humans but they are toxic to some species of plants if growing within a certain range of the tree so consider this if you are a gardener or homeowner.

Black Walnut Tree

I actually have a question. What would make very Mature trees not produce nuts? We have about a dozen and for some reason this year some trees have none.

TAP THEM FOR SYRUP

I tapped three of my walnut trees for sap to make syrup last spring for the first time. The syrup is like maple, but with a butterscotchy overtone. Delicious. I plan to buy more taps and tap more trees next spring. They do not yield as much as maple trees, but since I have no maples but plenty of walnuts, I'll happily make due with what I have. Squirrels bury the nuts, starting many new trees each year. Just cut down the ones you don't want to grow before they get too big. You may have to cut them down a few times before they stop coming back.

This article mentioned that tomatoes don't do well under walnut trees, but I read elsewhere that they are juglone tolerant. So I have a few tomato plants within the drip line of some maybe 15 year old trees. "Mrs. Maxwell's" variety is doing the best so far, "Delicious" not so good, and "Amish Paste" somewhere in between. A hot pepper plant is also doing well, as are two elderberry bushes I just got this year.

black walnut trees

I have been enjoying the comments about black walnut trees. We have a lot of them here in central Pennsylvania and all the comments, pro and con, are true! They are messy, dangerous and delicious! I am continually pulling baby walnut trees out of my garden beds because the squirrels seem to think it's a good place to 'plant' them. I've watched them do it. They will then put a nice leaf over the spot and pat it down. I have to say that I love squirrels...but am not too happy about walnut trees coming up in my garden.

Poisonous to horses

Be aware that if you live in a rural area, that Black Walnut is highly toxic to horses. Even if shavings get in their stall, it can kill them.

Black Walnut Trees

Besides collecting the walnuts, we also tap our black walnut trees to make syrup. It has a more nuanced flavor than sugar maple syrup and is one more way to utilize our trees.

Black Walnut Trees

We have 4 Black Walnut Trees in our yard. We do love / hate them! The nuts are ankle breakers if not collected. I have a "walnut wizard" which makes picking them up SO easy! I couldn't co-exist without it! The hulls are dangerous. My hubby blasted them all off with a pressure washer one year and the next day he was covered in acid burns. He had to seek medical care and was on allergy meds & burn cream for a week. His Dr. said he had never seen anything like it! BEWARE THE HULLS!!!

Black Walnuts

I grew up on a farm in Virginia with a black walnut tree in the front yard. We would gather the green nuts and pile them under the tree. When the hulls turned black, we would put them in the driveway and my father would run over them with his truck to break the hulls off. Then we would spread them out to dry and crack them open with a hammer on a good hard rock. Yes we went to school with stained hands but so did other kids. We all knew this was stain and not dirt, so no one cared. They also knew it was because we were doing our part to help the family. Those were good memories!

Love My Trees

In a small Northeast Central Indiana town we have a Black Locust, a Black Walnut & an Ash in a row between two houses. Our neighbor is scared to death every time a Walnut drops on his house. They can be dangerous when they drop. I had one break a windshield on our car while driving a couple of years ago. Our Squirrels seriously enjoy them & since I supplement their diets with peanuts & bird seed during the rest of the year, we enjoy having them around as well. Before I just mowed them each year but now that I use a Battery powered SunJoe mower, I rake the nuts 1st (less power than a gas mower). Never a problem with the roots or Juglone. Our property is a Certified Wildlife Habitat through the NWF (National Wildlife Foundation) & the tree provides part of the requirements for certification. Not my favorite tree because of the clean up work but they provide great shade, critter habitat & are otherwise maintenance free. I think I'll keep it!

Black Walnut Trees and Pear Trees

I would have to say that the comment about the Walnut tree roots producing jaglone and it inhibiting other plants from growing is slightly miss leading at best. I have a Pear tree which produces fruit that is partially hollow and it has a Walnut tree growing out of the hollow spot at its base that also produces fruit. The pear tree is the oldest of the two and has been around at least 40-50 years the walnut tree has been there for at least 25-30 of those years.

Black walnut trees

They are toxic to horses! The leaves and the nuts and the grass underneath the tree.

I Would Share My Opinion But I'd Get Censored

Comments on black walnut trees ??? I'd rather be eaten alive by fire ants than to ever buy another house with them anywhere near it. We have a squirrel infestation now and they destroy everything. They chew those shells into a summer long rain of gooey bits just coating the yard and house. It stains everything and looks like green bird dung. The nuts are ankle breakers and I have to hire a kid to come and clean my deck once a week, but i can only use it for a day afterwards before it's covered again. I despise these trees. Worse thing on earth to have within a mile of your dwelling. I'd love to buzz the last plank of the last walnut tree through a planer !!

Black walnuts are a pain!

I have 3 large Black walnuts near where my driveway meets the street (neighbors have others, also near the street). When the nuts drop, the go 'splack!' onto the pavement; then, when cars drive over and flatten them, they become ugly black 'pancakes' that last forever on the street. I used to broom them off to the road side as soon as possible to avoid that, but my disabilities have restricted my neighborly actions. I tried pickling them one year; gathered, and put in baths of brine, covered for a couple of weeks. Result: A lot of mess, wasted water, brining salt, and time. This year, I'll consider picking up a few and following the guidance posted in this article. I do love the shade, however; helps reduce my A/C use.

Black Walnut Tree

I've had a black walnut tree hovering over my backyard for 25 years now. Squirrels have built tribes surrounding it. The only drawback? When those suckers fall? It sounds like gunshots on the patio table. They float in my swimming pool. However, I love it and will continue to nurture it. I'm going to try to harvest some and use them in my cooking.

Thought it was something else

We just had a 60+ ft Black Walnut tree cut down. We didn't want to because it shaded 2/3 of our house and yard in the Texas summers. The rings on the inside of this tree made it at least 100 years old!

Thought it was a chestnut tree

I lived in my house in Toronto Canada for 10 years and thought her backyard tree was a chestnut tree I just found out it is a black walnut tree. The walnuts are still a golf ball size and wondering when they will become the baseball size tree is about 10 years old.

Get rid of black walnut

How hard is it to destroy this tree? I have one, about 10ft tall, growing between 2 houses approx 10 from each other. Obviously the roots will damage both foundations. Help!
(If this tree can be moved, I'm happy to try, but it's a smallish residential lot.)

Black Walnut

I was looking up the black walnut to understand how long the tree survives. I have a very large one towering over my garden and my neighbours garden from 2 doors over in the beaches area of Toronto. Everything I read about it in the almanac rings true. I’m amazed at the 250 year potential age. My neighbour hood is 100 years old and over the last 15 years all the Norway maples have died and only the black walnuts remain thankfully giving shade and a beautiful green coverage. Walnuts can be nigh on lethal but the squirrels tidy them up pretty quickly. Good to know that the tree cover will remain for potentially another 100 years.

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