The Monday Garden, January 30, 2005, Issue 149
Eco-gardening at its best
Our native black walnuts are forest trees; they like to stretch their roots in deep, rich, moist, acidy forest soil. However, even the babies can’t tolerate shade, so new black walnut trees have trouble getting started except in clearings and at the forest edge. Further, the nuts are so large and heavy that the squirrels can’t transport them very far. Thus, the only way for the seeds to be disbursed over long distances is by water (hence, the prevalence of black walnuts along forest streams) and by human.
picture: mature black walnut with the back of the new courthouse in the background (Juglans nigraa), Bedford Street Stamford, CT January 2004
While young black walnuts (Juglans nigra) can be easily confused with the alien ailanthus, and with other trees with palm-like pinnately compound leaves, such as the native staghorn sumac, ash, and locust, there’s no mistaking the lime green “golf ball” nuts on teenage and mature black walnut trees.
picture: mature black walnut (Juglans nigraa), Bedford Street Stamford, CT September 2004
Black walnuts have developed two strategies to help over come these reproductive limits. First, the young trees grow fast (for a hardwood tree, that is). This trait helps a sapling take advantage of a short-term gap in the forest canopy or other shade source. Second, like the ailanthus, the black walnut is an allelopath. It produces chemicals that literally kill off competing plants. Interestingly, the chemicals that black walnuts produce are particularly poisonous to the solanaceae family (tomatoes and kin- see Issue 117), several other garden vegetables, conifers, and the malus family (apple, hawthorn, serviceberry, etc). The conifers make sense because juniper, for example, would be an edge-of-forest competitor. However, as for the others, who knows what happened a million years ago when these survival traits were evolving?
In pre-Columbian times, there were absolutely HUGE black walnuts, 100 to 150 feet, gracing the eastern American forest from Zone 4 to Zone 8, west through the Great Plains. These mature black walnuts were massive, long-lived beings, standing tall and straight with a high, small crown in the forest; and spreading wide as a white oak when alone in a meadow. However, the dark, hard, satin grained lumber was so prized by the European settlers that, sadly, almost all of the old growth trees were chopped down long ago. The wood continues to be so valued today that medium-size trees are cut down to use for veneer – crafting objects out of solid black walnut is a thing of our colony past.
picture: massive, spreading form of a mature open-grown black walnut. Stamford CT January 2005.
Despite the wonders of the wood, the nuts may be the tree’s best and worst feature. The nut meats are delicious—we like them in deserts; squirrels and mice take theirs plain. However, getting to the meat is a challenge. The thick, soft outer shell covering which starts out lime green and ages to dark brown, contains a dye which will stain you hands and clothes. It’s not generally harmful to people but it does contain the black walnut’s allelopathic chemicals so don’t throw the husks in the compost heap. Then, inside the husk is a very, very hard shell. Try a hammer.
picture: fallen black walnuts, striped of the outer husk; one has been gnawed open by a squirrel or a mouse. Stamford CT Winter 2004-05
The other problem with the nuts is that there are so many of them on an adult tree. Generally, many more than a family (and the neighborhood squirrels) can use, and what do you do with the rest? Remember, also that the nuts are big – do not plant this tree close to your house unless you’d like your decedents to stay awake nights listening to the thud of walnuts hitting the roof.
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pictures: detail of nuts which persist on the branches after the leaves have fallen.
IDENTIFICATION: It’s easy to distinguish black walnuts from other trees when the signature nuts are present (which is most of the time, if you count the shells on the ground). With a little more information, you can tell the difference the rest of time, too.
FORM AND BARK: The young black walnut trees have the same up-reaching, blunt, twigless branches like ailanthus and staghorn sumac. However, there are clear differences. First, the black walnut develops rough, craggy back at a very young age, while ailanthus and staghorn sumac are still smooth-ish with prominent lenticels (bark pores). The mature black walnuts have a craggy, spreading nut tree shape—staghorn sumac don’t get this big and ailanthus are always up-swept, and comparatively lithe and curvy. The mature black walnuts have very deeply furrowed bark. Also, the bark is much darker than that of mature ailanthus and staghorn sumac.
picture: believe it or not; the young tree on the left is a black walnut and the one of the right is a slightly older ailanthus.
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pictures: bark of 3”, 12” and 24” diameter black walnut trunks. Note that even the young 3” tree to the left has very rough bark. The base of tree to the right is encircled with an invasive euonymus. Unfortunately, even the black walnut allelopathic properties don’t deter this unwanted alien.
TWIG AND BUD: the winter twig and bud are very different from ailanthus and staghorn sumac. As you recall from last week, the ailanthus and staghorn sumac winter twigs are smooth and blunt with knobby buds, prominent lenticels, and large, flattish leaf scars, the black walnut has whitefish –grayish furry buds and 3-lobed leaf scars often called “monkey faces”.
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pictures: close up of bud and of prior years’ leaf scars Stamford CT January 2005
Picture: buds and leaf scars. January 2005.
LEAVES: while the leaves of staghorn sumac, ailanthus, black walnut, ash, etc, look much alike for a distance, close up, the leaf detailing is different. Like ailanthus and staghorn sumac, the black walnut’s numerous stemless leaflets are opposite on the long leaf stalk and the leaf stalks are alternate.
However, there’s one leaf detail that only the black walnut has: a tiny notch on one side of the midrib just where the leaflet attaches to the stalk. In addition, the leaflets are toothed, with paler, hairy undersides; this rules out ailanthus which has a smooth leaf margin with a single lobe at the leaf’s bottom. The teeth are much finer than the sumac’s. In addition, the black walnut often lacks the single, terminal leaflet that ailanthus and staghorn sumac always have.
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pictures: leaf detail; note the notch at the base of the leaflet, the fish tail like curve of the leaflets and the missing terminal leaf. (Some black walnuts have a small terminal leaf).
picture: in midsummer, the black walnut provides dappled shade. Stamford CT 2004
Wildlife: For reasons unknown, the eastern screech owl prefers to roost in black walnuts (perhaps they’re attracted by the mice nibbling on fallen nuts). Several birds are said to eat the nuts as do squirrels and mice. (Query: how do the birds get the nuts open?). Deer, rabbit, and mice will browse the young trees.
Photo credits: Sue Sweeney
© Sue Sweeney 2005
Comments (21)
Be careful of driving under Black Walnut trees when it's windy and the nuts are ready to fall! This past autumn I was driving along a back road and suddenly ==BAM!!== A single nut fell from a Black Walnut tree that was hanging over the road as I sped by, and impacted upon the front windshield of my car. Sounded like a gunshot. That single nut was hard enough to smash the entire front windshield - cracks clear across!
Posted by Walter Muma | January 30, 2005 4:46 PM
Posted on January 30, 2005 16:46
Greetings. I really love the image and descriptions on your site! At least two of your images have been uploaded to Wikipedia for use in articles. (I'm a Wikipedia volunteer.) In order for us to keep the images, however, we'll have to know whether you agree to let us use them under the terms of the Wikipedia copyright.
http://en.wikipedia.org/wiki/Wikipedia_Copyright
If it's alright for us to use some of your images, please e-mail me at MichaelQWaddell@gmail.com, but please remove the Q. (Yes, I'm paranoid about spam.) If I don't hear from you, we'll have to delete the images.
Thanks,
Michael
Posted by Michael Waddell | February 3, 2005 2:50 PM
Posted on February 3, 2005 14:50
I live in Michigan and have recently purchased a home and adopted two large (50+ years old)black walnut trees. They are beautiful and provide great shade. However, the squirrels are a HUGE problem in fall. They get into just about anything the nuts are collected in for disposal. I waste hours and hours picking up the nuts only to have them back out on the lawn or patio. If anybody has advice on composting these nuts underground or otherwise it would be much appreciated!
Posted by J. Butkovich | August 22, 2005 3:53 PM
Posted on August 22, 2005 15:53
I suggest leaving a few out for the squirrels to satisfy their little thieving hearts, and putting the rest in sealed garbage cans until you can dispose of them . The soft outer shells of the nuts probably carry the allelopathic (herbicidal) chemicals for which the black walnut is famous so putting them in the compost or burying them, might kill things that you're trying to grow.
You could see if you could find a human who wants to come collect them -- the nuts are delicious and the shells are great for hand dying. When I was a kid in Duchess County NY a family would drive all the way from NYC each fall to take home bags of the nuts from our big tree. You might trying posting it on freecycle or craig's list.
My father used to take the excess nut out along the fence lines, dig a hole by each fence post and drop in a basket full of nuts. Some of the nuts did grow into trees; the rest probably helped keep down some of the weeds.
Let me know if you find a solution that works for you.
Sue
Posted by S. W. Sweeney | September 15, 2005 7:21 AM
Posted on September 15, 2005 07:21
I have several black walnut trees on my place. while out looking for the nuts fallen from the tree, i have found other trees that do not look quite like a black walnut tree, but have nut that look similar but are smaller than my other blak walnuts. are these also black walnuts are is there another tree that produces nuts with the green outer husk and black juice inside? thanks for the help
Posted by Jason | October 9, 2005 9:05 AM
Posted on October 9, 2005 09:05
Living in the Northeast, I don't have that much experience with walnut trees beside the black walnut. However, botanists have counted about 100 varieties of the black walnut itself and, depending on where you live in the country, it might be another type of similar-looking walnut, such as the little walnut. Here's the Fed's listing of the most common native and naturalized walnuts.
http://plants.usda.gov/cgi_bin/topics.cgi?earl=plant_profile.cgi&symbol=JUNI
Then there's always the possibility that it could also be a foreign import -- it is said that the husks of the English walnuts are used for dye as we use the black walnut.
If you want to make an identification, take a close look at a complete compound leaf, the outside and inside of the nut, the tree's bark, the tree's branch structure, and the buds. Then see how all these items compare with what you know to be a black walnut.
Hope this helps get you started
Sue
Posted by S. W. Sweeney | October 10, 2005 2:04 PM
Posted on October 10, 2005 14:04
We have a home in Newberry, Florida. Our property has walnut trees and after reading your
web site, we now know we have a fully mature
black walnut tree. Do we just hammer the inner shell and then eat the nut? I have a dear friend who makes a delicious black walnut cake at Xmas time. Is it worth making a phone call to her and let her know I have fresh nuts for the picking?
Posted by Fran | October 24, 2005 6:03 PM
Posted on October 24, 2005 18:03
Lucky you.
Yes, just crack the black walnuts open. We had a giant black walnut when I was a child and I can still remember how good the nuts were in cakes and breads.
Black walnuts aren't all that rare but your cooking friend might appreciate a source that she knows is pesticide-free and, better yet, might share more of the finished product with you.
Enjoy
Sue
Posted by S. W. Sweeney | October 26, 2005 7:48 AM
Posted on October 26, 2005 07:48
I currently have 5 Black Walnuts in my back yard. Origionally I thought that they would be wonderful. Then my grass started dieing, my shrubs wouldn't live. Now I have cut them down and am doing a research paper for school about the best way to remove and dispose of these trees. If anyone has any suggestions for removal short of a backhoe I would be very interesting in hearing about it.
Posted by Horticulture Student | November 2, 2005 10:27 PM
Posted on November 2, 2005 22:27
Living in the Northwest, Black Walnuts are an easily adaptable tree that are great, unless you want to grow shrubs or grass. Then it becomes much harder. I have 5 that I am currently trying to remove with out the help of a backhoe and would appreciate any information regarding this. I am also doing a research paper on this subject for school.
Posted by Hort Student | November 2, 2005 10:33 PM
Posted on November 2, 2005 22:33
Anita -- thanks for vising my site and thanks for posting your comment. Since the black walnut spreads its allelopathic chemicals through the soil , I'm curious about the condition of the soil after the tree is removed.
Is the reason for the backhoe, trying to remove the tree's underground parts and to decontaminate the soil?
Also, I'd be very interested in the results of your study when you've completed it.
Good luck with your project
Sue
Posted by S. W. Sweeney | November 3, 2005 5:40 PM
Posted on November 3, 2005 17:40
I recently read that black wlanuts shoudn't be planted near water as the allelopathic chemicals are bad for fish
Sue
Posted by S. W. Sweeney | February 8, 2006 4:41 PM
Posted on February 8, 2006 16:41
How does a consumer judge the age of black walnut meats and cracked shells?
Posted by Patt Jordan | February 10, 2006 4:19 PM
Posted on February 10, 2006 16:19
Patt -- are you trying to figure out which ones are still good to eat?
I'm not an expert but remember something about this from my childhood. For eating, it was crack the nuts open, and then check each one to see if the meat was still plump, free of visible rot or fungus, and smelled good. Once the hard shell is cracked, the nut meats will start to dry out and/or rot. The nut meats, though, can be frozen.
Does this help?
Sue
Posted by S. W. Sweeney | February 11, 2006 4:52 PM
Posted on February 11, 2006 16:52
As a resident of Pennsylvania I am interested in establishing a grove of black walnut trees. Where can I get advice, such as suitable land and climate, soils, marketability?
Posted by Bill | April 23, 2006 2:37 PM
Posted on April 23, 2006 14:37
Bill -- I can hear your squirrels cheering already. Here are some resources that I trust:
The US Forest Service http://www.na.fs.fed.us/pubs/silvics_manual/volume_2/juglans/nigra.htm
Virginia Tech http://www.sfp.forprod.vt.edu/factsheets/walnut.pdf
U of Minn: http://www.extension.umn.edu/distribution/naturalresources/DD0505.html
Ohio Dept of Nat Res. http://www.ohiodnr.com/forestry/trees/walnut_black.htm
U of Missouri http://muextension.missouri.edu/explore/agguides/forestry/g05020.htm
Kansas Forest service http://www.kansasforests.org/conservation/deciduous/blackwalnut.shtml
The best search words seem to be "black walnut" + "forestry". Before making this investment, I'd want to read up as best I could about what the experts like those above say. I'd then also contact my local agricultural extension service and my state land grant college to see what additional help they could offer.
Good luck
Sue
Posted by S. W. Sweeney | April 23, 2006 7:05 PM
Posted on April 23, 2006 19:05
Bill -- If you search at Amazon.com under "Nut trees" there are several interesting looking titles including:
Growing Family Fruit and Nut Trees - comments indicate that this would be a good starter book
Nut-tree propagation (Farmers' bulletin / United States Department of Agriculture) (Farmers' bulletin / United States Department of Agriculture) -- watch out, though, the USA gov't and main stream agriculturists recommend the use of chemicals that many of us find unhealthy in the extreme.
There are probably text books (e.g from forestry and/or ag school) on the subject as well but they'd require a little more digging and could be a bit technical.
What I think is very important, in addition to site selection and proper planting, is getting the first few years of pruning just right. I know with fruit trees that there are conflicting thoughts on what "just right" means. I suspect that this is also true of nut trees, so I'd suggest reading widely on pruning so you can make up your own mind. Lee Reich's pruning book is a good overall starter.
The same applies for the basics on how to plant the tree -- there are conflicting schools of thought and there has been a lot of change in the past few years. So I'd read a few books, and search the web for newer information.
Also, in my view it would be most prudent if you could go "organic" or as close to certified organic as possible -- long term, this could make a difference in the profitability. Also you want to go a natural as possible -- lots of mulch, and organic matter on top of the ground for the insects and worms to dig in for you, no pesticides, as little site prep and soil amendments as possible, and no extra water after the first two years.
BTW: you can support the work of TheMondayGarden.com if you make your Amazon.com purchases via the Amazon search box on the site's book store page. http://www.inmygarden.org/archives/about_themondaygardencom/the_book_store/
Hope this helps
Sue
Posted by S. W. Sweeney | May 1, 2006 5:10 PM
Posted on May 1, 2006 17:10
I have recently purchased a home in Upstate New York and have two black walnut trees in my front yard. I am interested in having them removed. Someone mentioned they are valuable and there is probably someone out there that would like to purchase them. I am very interested in having these trees "relocated". Who would I contact about this?
Posted by Madelyn McCarthy | May 19, 2006 7:49 PM
Posted on May 19, 2006 19:49
Madelyn--
The wood can be valuable. Moving a mature tree is very risky. If you want to see if someone would buy the tree for replanting, contact your local arborist. If you want to sell the wood, your local lumber company could probably give you the name of a company that harvests trees.
Hope this helps
Sue
Posted by S. W. Sweeney | May 29, 2006 12:58 PM
Posted on May 29, 2006 12:58
Hi
Great info on your website. I was able to identify the mature black walnut on my property. Am I correct that they produce nuts every year? Also, would this mature tree be harming the cedar hedge directly below it?
Thanks
Karla
Posted by Karla Buckborough | July 9, 2006 7:56 PM
Posted on July 9, 2006 19:56
Karla --
The black walnut will bless you with nuts every year; it could be more in alternate years but definitely enough each year to make your squirrels happy and leave you enough for a cake or two or three or four....
The tree's allelopathic qualities are reported to affect conifers. As the tree grows, increased shade and competition for water might be an issue for the hedge as well and are easier to address (water more a bit more often, thin out some tree branches).
Sue
Posted by S. W. Sweeney | July 24, 2006 3:26 PM
Posted on July 24, 2006 15:26