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Companion plants that tolerate black walnut tree toxicity

Jan 24, 2013 -
   
  Companion plants that tolerate black walnut tree toxicity
Glory of the Snow (Chionodoxa forbesii) is a fall-planted bulb that grows happily under any walnut tree.
 
   

Walnut trees are fruitful and beautiful. I love to sit in the shade of one of my walnut trees and look out over the sloping garden. In our new video Tricia shows you how to care for and prune walnut trees.

walnut orchard

Walnut trees definitely like their own space, and can be bad neighbors to certain plants. Find out the best companion plants for walnuts.

Black walnut tree toxicity

Black walnut trees load their roots, buds, and nut hulls with the juglone toxin (leaves and stems have smaller amounts of juglone). The toxin seeps into the soil and susceptible companion plants will turn yellow, wilt, and sometimes die. The University of Missouri Extension notes that a characteristic symptom is the browning of inner stem tissue.

But wait, you say, I don’t have a black walnut tree. Actually, most walnut trees are grown on black walnut rootstock these days, therefore the root system is likely to be rich in juglone. The soil under the canopy of the tree will have the highest concentration of juglone due to the combined effects of the roots, along with fallen leaves, hulls, and shells that are lying on the ground. Picking up this litter is good “orchard sanitation” for many Integrated Pest Management reasons, including decreasing the amount of juglone.

franquette walnuts

Companion plants for black walnut trees

Purdue University has informal lists of plants that tolerate juglone and those that are sensitive to it. Choose from the following list for best results in planting near black walnut trees or walnut trees grown on black walnut rootstock. Follow these guidelines for planting within the dripline of the tree and, according to the University of Wisconsin, up to 50’-80’ from the trunk. Naturally you need to consider the sun and shade requirements of the plants, as well.

Vegetables: lima bean; snap bean; beet; carrot; corn; melon; onion; parsnip; squash.

Fruits: black raspberry, cherry.

Landscape plants: arborvitae; autumn olive; red cedar; catalpa; clematis; crabapple; daphne; elm; euonymous (burning bush); forsythia; hawthorn; hemlock; hickory; honeysuckle; junipers; black locust; Japanese maple; maple (most); oak; pachysandra; pawpaw; persimmon; redbud; rose of sharon; wild rose; sycamore; viburnum (most); Virginia creeper.

Flowers and herbaceous plants: astilbe; bee balm; begonia; bellflower; bergamot; bloodroot; Kentucky bluegrass; Spanish bluebell; Virginia bluebell; bugleweed; chrysanthemum (some); coral bells; cranesbill geranium; crocus; Shasta daisy; daylily; Dutchman’s breeches; ferns; wild ginger; glory-of-the-snow; muscari (grape hyacinth); grasses (most); orange hawkweed; herb Robert; hollyhock; hosta (many); hyacinth; Siberian iris; Jack-in-the­ pulpit; Jacob’s ladder; Jerusalem artichoke; lamb’s ear; leopard’s bane; lungwort; mayapple; merrybells; morning glory; narcissus (some); pansy; peony (some); phlox; poison ivy; pot marigold; polyanthus primrose; snowdrop; Solomon’s seal; spiderwort; spring beauty; Siberian squill; stonecrop; sundrop; sweet Cicely; sweet woodruff; trillium; tulip; violet; Virginia waterleaf; winter aconite; zinnia.

Plants that are sensitive to black walnut tree toxicity

Vegetables: asparagus, cabbage, eggplant, pepper, potato, rhubarb, tomato.

Fruits: apple, blackberry, blueberry, pear.

Landscape plants: black alder; azalea; basswood; white birch; ornamental cherries; red chokeberry; hackberry; Amur honeysuckle; hydrangea; Japanese larch; lespedeza; lilac; saucer magnolia; silver maple; mountain laurel; pear; loblolly pine; mugo pine; red pine; scotch pine; white pine; potentilla; privet; rhododendron; Norway spruce; viburnum (few); yew.

Flowers and herbaceous plants: autumn crocus (Colchicum); blue wild indigo (Baptisia); chrysanthemum (some); columbine; hydrangea; lily; narcissus (some); peony (some); petunia; tobacco.

Field crops: alfalfa; crimson clover; tobacco.

Tip: This does not mean you can’t compost black walnut leaves. According to Ohio State University Extension, “walnut leaves can be composted because the toxin breaks down when exposed to air, water and bacteria. The toxic effect can be degraded in two to four weeks.” If you do compost the leaves, put them in a separate compost pile and do not spread the resulting compost on plants that are on the sensitive list.

For more information: The go-to book for anyone growing nut and fruit trees in California is the UC Davis publication, The Home Orchard.

Add some walnut trees to your property and create a beautiful landscape with these companion plants that tolerate toxicity.


Categories: Nut Trees, Edible Landscaping


Celena Polena Says:
Feb 19th, 2013 at 3:17 pm

We have cut down a dying black walnut tree. We want to plant mandarins in the area of the stump. Is it possible? Hww long will toxicity remain in the soil?

Charlotte from Peaceful Valley Says:
Mar 4th, 2013 at 1:45 pm

Celena, The black walnut stump will still be creating a toxic environment for all plants that are not tolerant of the chemical (juglone) they introduce to the soil.  The toxicity extends well past the year of the tree’s death and if the stump is allowed to remain, the toxin will still be released into the soil from the degrading root system. 

Citrus is not on the list of tolerant plants, unfortunately. It would be safest to consider another site, or possibly use above ground containers in the area if no other spot is possible.

Becky Says:
Mar 12th, 2013 at 10:10 am

The list above has crabapple in both lists? Which is correct, I have a crabapple tree coming to plant in the same yard as a fairly large black walnut tree. Will it die?

Charlotte from Peaceful Valley Says:
Mar 12th, 2013 at 12:08 pm

Becky, Thanks for spotting that. Crabapple is resistant to juglone, according to the U. of Minn. http://www.extension.umn.edu/yardandgarden/ygbriefs/h407blkwal-tox.html I have edited our lists.

Jennifer Straw Says:
Apr 13th, 2013 at 8:19 am

Are liquid ambers on the companion or sensitive list? How far away from a lime tree do you recommend planting a black walnut? Also, oaks and redwoods? I live in the Santa Cruz Mountains, wherewith lots of oaks and redwoods

Thanks, Jennifer

Charlotte from Peaceful Valley Says:
Apr 13th, 2013 at 5:46 pm

Jennifer, All I can say for sure is that Purdue University lists oak as a tree that will tolerate juglone.

Tanya Says:
Apr 27th, 2013 at 1:53 pm

what about evergreens? I have ten fairly large evergreens along my fence line. I just bought a black walnut ash. I was told not to put it near my plants. The chosen spot is far from the flower gardens - in the back of the yard but down the line from the evergreens. Should I chance it and plant it or not? My evergreens are needed screening from neighbors.

Charlotte from Peaceful Valley Says:
Apr 30th, 2013 at 4:25 pm

Tanya, It depends on the type of evergreen.  The only evergreens listed as tolerant are some junipers (Chinese and Common), Red Cedar, Arborvitae and Eastern Hemlock.

Susan Schwaab Says:
May 19th, 2013 at 5:48 pm

Can I plant red raspberry plants near a black walnut?
What about kitchen herbs such as basil, thyme, etc?

Charlotte from Peaceful Valley Says:
May 22nd, 2013 at 11:22 am

Susan, Raspberries can be pretty hardy, but they are not on any list of plants that are compatible with black walnut.

Some herbs do tolerate black walnut, but they are more obscure kinds like bee balm and peppermint.  Thyme is usually pretty tolerant and might be worth a try.

 

AP Says:
May 28th, 2013 at 10:11 am

Are California walnuts as toxic as the others?
Thanks,

Charlotte from Peaceful Valley Says:
Jun 7th, 2013 at 3:31 pm

AP, The English walnut also has juglone, but not in the concentration of the Black Walnut, which is the notorious problem. It does not have the same companion issues, but it should be kept in mind and neighboring plants should be given some distance if they are sensitive.

Nancy Hatcher Says:
Jun 14th, 2013 at 7:48 am

What about Itoh peonies?  Just planted 2 that are about 25’ from a black walnut. 

I’ve read that you can’t put sensitive plants within 60’ of a black walnut.  I did plant blueberries about 20-25’ from a black walnut.  I’ve lost all but 2 and they are struggling.  The leaves have turned a bit yellow and the veins are showing.  Is this from the walnut?  I did plant them with peat moss two years ago and have added some as mulch.  If it is the walnut is it too late to move the berries?  If not, should I try to shake off as much of the dirt as I can or will that stress the blueberries more?

Thanks!

Charlotte from Peaceful Valley Says:
Jun 14th, 2013 at 10:10 am

Nancy, The universities are not clear about which peonies are sensitive to black walnuts. You might want to contact your Itoh peony grower and ask them if they have any experience with growing near black walnuts.

As for the blueberries, your are right to move them. Give the blueberries a good shake, but don’t try to pick off every speck of soil. To reduce transplant stress use our Organic Liquid Kelp as a soil soak at replanting time, and then as a foliar feed on the blueberries—the kelp is a tonic rather than a fertilizer so you cannot overdo it.

John Winterkorn Says:
Jun 20th, 2013 at 10:23 am

I want to plant some dogwood trees near mature walnut trees.  Will they do OK.
    Thanks,

Charlotte from Peaceful Valley Says:
Jun 20th, 2013 at 3:06 pm

John, Looks like you are probably in luck! The Morton Arboretum lists some shrubby cousins of the dogwood as tolerant of juglone. The most common dogwood to plant is Cornus florida, and the native California dogwood is Cornus californica. You will see their Cornus relatives here under Shrubs http://www.mortonarb.org/tree-plant-advice/article/887/plants-tolerant-of-black-walnut-toxicity.html

janeisgreen Says:
Jun 26th, 2013 at 5:54 am

I’m in Ontario, Canada, and have Black walnuts surrounding my entire property. First, at least in Canada, do NOT plant Autumn Olive—it’s an invasive alien here.

Secondly, I’m growing lots of things, some easily and some using straw bales or the “Ruth Stout” method. I have three different types of native Dogwoods, native Elderberries, native Black Raspberries, Haskap berries, gooseberries, native Chokecherries, enormous old Spruce trees, willows, etc., etc. I’m also growing tomatoes in straw successfully, although the ones in containers are growing faster. Most native flowering plants grow fine, also.

Charlotte from Peaceful Valley Says:
Jun 26th, 2013 at 12:07 pm

janeisgreen, Thank you for the report from your garden!

Kathy Says:
Jun 30th, 2013 at 8:41 am

Does anyone know if Japanese Forest Grass is Juglone tolerant?

Ian Says:
Jul 8th, 2013 at 5:07 am

What type of cover crops or forage for chickens can I plant under a black walnut. I see grasses are good, so I assume wheat or rye, but how about summer covers like Buckwheat? Also will a wildflower mix do well? My chickens have denuded the area under the tree and I have moved them. Would maybe like something for them to eat when I put them back.

Charlotte from Peaceful Valley Says:
Jul 9th, 2013 at 4:16 pm

Ian, We don’t have a plant list that is more extensive than the information here—so going with grasses seems to be your best bet but beyond that you should try cover crops that do well in your zone and season.

The chickens would be eating the wildflowers before they had a chance to bloom, wouldn’t they?

Sadly, alfalfa and clover do NOT do well with black walnut/juglone, so you should not plant our Omega-3 Chicken Forage Blend here, but do try it elsewhere in your garden http://www.groworganic.com/omega-3-chicken-forage-blend-irrigated.html Let us know which grasses work well in the location.

Charlotte from Peaceful Valley Says:
Jul 9th, 2013 at 4:24 pm

Kathy, We don’t know about Japanese Forest Grass and juglone. The list says “most grasses” are tolerant of juglone, so perhaps you can do an experiment and let us all know?

Mark Says:
Jul 29th, 2013 at 11:49 am

I grew a garlic patch close to a Black Walnut tree. It seemed to grow fairly well. Will the Juglone affect the garlic in any way (making it toxic)? Would the Juglone help the garlic by killing of some of the harmful nematodes that have been killing some garlic root systmes?

Charlotte from Peaceful Valley Says:
Aug 7th, 2013 at 2:57 pm

Mark, Garlic will probably do fine in spite of the juglone. Onions, from the same allium family, are on the tolerant list. The juglone does not, as far as I can tell, pass along any toxicity—it simply hampers the growth of plants that are sensitive to it. The interaction of juglone with susceptible plants is described as “Plants sensitive to juglone show signs of wilting, yellow leaves, stunted or slow growth, and eventually death.”

I have to get rid of invasive horseradish plants. Says:
Oct 10th, 2013 at 7:45 am

Cindy

Charlotte from Peaceful Valley Says:
Oct 11th, 2013 at 1:59 pm

Cindy, Yes, that’s an invasive plant, but the good news is that this IS the time of year to harvest it. When you dig up the roots try to get all the lateral roots too, and you may succeed in having a horseradish-free garden. If it returns, keep digging and one of these years you’ll win. If you miss eating it after a while, then grow it in a container.

Tere Says:
Oct 28th, 2013 at 12:03 pm

Charlotte, I have lots of black walnut stumps that I would like to use for edible mushroom cultivation. Specifically, Chicken Mushroom and King mushrooms Is it safe or does the toxin continue into the mushroom?

Stephanie Brown Says:
Dec 20th, 2013 at 10:25 am

Tere, Juglone is present in every part of the plant so unless someone eating the mushrooms is allergic to walnuts it should be just fine. Juglone is a natural antimicrobial agent so I’m not sure if the mushrooms would take right away, but I found no research that said not to use them. Hopefully that helps.

Katie Says:
Feb 10th, 2014 at 12:12 pm

My son wants to make cutting boards using walnut.  Can the sawdust be composted - or would we be better off making a separate compost pile for this?  also, does the wood pass along any toxicity in the cutting board?
Thanks.

Stephanie Brown Says:
Feb 10th, 2014 at 4:25 pm

Hello Katie, Yes I would make a separate compost pile with walnut saw dust and don’t use it on sensitive plants. The composting process will reduce the juglone quite a bit but a might release a little bit still. The cutting boards will be beautiful and safe. You get quite a high dose of juglone from eating walnuts (English walnuts have less than Black walnuts). In fact, in the case of pecans, the juglone content of the nut is two to three times higher than the trunk.

Sandra Says:
Feb 25th, 2014 at 2:25 am

What about quinoa? thanks

Sanda anderson Says:
Feb 25th, 2014 at 8:45 am

Hello Charlotte,
Would quinoa tolerate walnut toxicity? Thanks in advance

Stephanie Brown Says:
Feb 25th, 2014 at 12:44 pm

Hello Sanda,
I was unable to find any research that said it grew under walnuts or it didn’t. I’d say it’s worth a bit of trial and error to see. If lambsquarter grows under walnuts than the quinoa would do well since they are very close relatives.

Sarah Says:
Mar 10th, 2014 at 12:37 pm

I can’t find hazelnut or filberts on any of the lists, as companion or sensitive. We have a couple black walnuts on our property and would love to add a couple of native hazelnuts. But it makes no sense if they will die. Do you have any useful information on this?

Stephanie Brown Says:
Mar 11th, 2014 at 8:33 am

Hello Sarah,

According to Penn State American Hazelnuts (Corylus amaricana) the native hazelnut are on the tolerant of juglone list. http://extension.psu.edu/plants/gardening/fact-sheets/trees-shrubs/landscaping-and-gardening-around-walnuts-and-other-juglone-producing-plants

Vicki Nash Says:
Mar 27th, 2014 at 8:43 am

I need to know what herbs specifcally mint or spearmint & dill and parsley

Stephanie Brown Says:
Apr 8th, 2014 at 10:41 am

Hello Vicki,
Yes, mint is on the tolerant of juglone list. I haven’t seen dill or parsley on either list. Juglone toxicity tolerance or sensitivity is an active area of study. All that to say, for many plants it’s just not known.

doot trolz Says:
Apr 23rd, 2014 at 7:59 am

we have deer and black walnut.  will lavender, gallardia, salvia, yarrow, and soapwort grow under black walnut?  The deer don’t eat those.  We have cone flowers, black-eyed susans and vinca, both walnut and deer resistant but would like to try something new. love this column!

Stephanie Brown Says:
Apr 23rd, 2014 at 9:42 am

Hello Doot,

Yarrow is known to be resistant to juglone. Lavender, gillardia, and salvia don’t appear on either list, so I’d say they’re worth a try. Some other juglone and deer resistant perennials I found are bluebells (Endymion sp.), Jack-in-the-pulpit, and daffodils. Good luck!

doot Says:
Apr 24th, 2014 at 7:23 am

Thanks so much!  We’ll give ‘em a try and let you know!

kevin prendergast Says:
Apr 27th, 2014 at 10:18 am

can i plant a decorative dappled willow tree near my 36 inch diameter black walnut tree ?  dappled willow would be planted 60 feet distance from walnut tree in a slightly raised bed.

Jackie Says:
Apr 28th, 2014 at 5:26 am

Daughter wants to know if lavender will grow near a walnut tree. Thank you in advance on your responding to this request.

Stephanie Brown Says:
Apr 28th, 2014 at 7:56 am

Hello Jackie,

Lavender isn’t on the sensitive or the tolerant list. Juglone sensitivity is an ongoing study, so it’s not known. I’d say get one plant and see if it does well.

Stephanie Brown Says:
Apr 28th, 2014 at 8:07 am

Hello Kevin,

Willows are on the tolerant list so it should be fine.

Molly Says:
May 17th, 2014 at 8:30 pm

Are there any rhododendrons that can tolerate black walnut? Mine has slowly killed off two! I do have good luck with peonies, hosta, ferns, and Japanese maples!

Stephanie Brown Says:
May 19th, 2014 at 9:05 am

Hello Molly,

Unfortunately, I don’t know of any rhododendrons that are tolerant of juglone. Rhodies are on the sensitive list.

Steve B Says:
Jun 19th, 2014 at 7:56 am

Love this article and the comments: really helpful.  We recently had a 75+ year Blk Walnut taken down and stump ground out and are looking to put a new tree in close proximity.  Sounds like Japanese maples and rosebuds are tolerant, but our wish list for new trees also includes dogwood and tricolor beech.  Has anyone had any experience with these and how they might tolerate juglone in the residual rotting root systems?  We are SE Pennsylvania area, and are looking forward to no longer having walnuts hit us and our cars in the nearby driveway.

Jeffrey Lodginski Says:
Jul 1st, 2014 at 11:23 am

Will healthy ferns about 4 to 5 feet tall survive lining near a black walnut tree?

Stephanie Brown Says:
Jul 2nd, 2014 at 10:30 am

Hello Jeffrey,

Yes, ferns have been observed to be tolerant to juglone.

Stephanie Brown Says:
Jul 2nd, 2014 at 10:34 am

Hello Steve,

Dogwoods are considered tolerant. I haven’t seen beech on one list or the other. The juglone will persist in the soil for a while as the roots decompose in the soil.

Karen Says:
Jul 23rd, 2014 at 4:26 pm

Hello I am wondering if aronia is tolerant of black walnut as well as the s. Nigra species of elderberry?

Suzanne Says:
Jul 25th, 2014 at 12:25 pm

According to information I found on the internet, Aronia is highly sensitive to juglone and should not be planted by a black walnut. I have found information on the Virginia Cooperative Extension (http://pubs.ext.vt.edu/430/430-021/430-021.html) that says elderberry is tolerant to growing near a black walnut.

Mary Says:
Jul 28th, 2014 at 8:09 pm

Wondering about herbs like basil, tarragon, oregano and lemon thyme? Will they be ok under the tree? Planted before i realized it was a black wanut tree in my new yard!

Suzanne Says:
Aug 1st, 2014 at 11:56 am

I have not found information regarding the herbs you are interested in planting. All the herbs you listed, except tarragon, prefer full sun so planting under a tree may not be the best idea.

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