Gardening with Killers

by Daisy

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One of the major challenges of urban gardening is finding the right space for your garden.  Ideally, a space that gets six to eight hours of sun each day, is conveniently located near a water supply, gardening equipment, and the gardener.

I’ve found that spot, just.  In my tree-filled yard, it’s the only place big enough and sunny enough to make a go of it.  Problem is, it’s flanked by two of the deadliest characters known to gardening:  black walnut trees.  Over sixty years old, they’re no pushovers.  Handsome, but terminally toxic to many of my favorite things including nightshades (tomatoes, potatoes, eggplant), as well as blueberries, blackberries, raspberries, asparagus, and rhubarb, among others.

It’s known as allelopathy, or when a plant exudes chemicals which kill or reduce the growth of surrounding plants.  In the case of the black walnut, it’s a chemical called juglone, and it’s most concentrated in the roots.  Everything growing within the root zone of my black walnut trees is subject to the effects of juglone, which can cause plants to yellow and wither.

I’ve considered hiring someone “to take care of my problem.”  But I can’t bring myself to do it.  Planted by my grandfather, they have a place here.  And luckily, I prefer raised bed gardening anyway.  Besides, the toxicity remains in the soil for many years even after the trees are gone, so cutting down the trees wouldn’t be of much help.  Also luckily, many plants completely ignore juglone, apparently, such as melons, beans, beets and even the black variety of raspberries.

I discovered recently when looking into putting a bird feeder at the edge of the garden that sunflowers and their seeds are also allelopathic.  So the feeder is going to be put further from the edge of the garden than I’d planned, and the sunflowers I was going to scatter among other flowers are going to have their own spot.

What challenges do you face in your urban/suburban yard?

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{ 25 comments… read them below or add one }

Q February 25, 2011 at 9:21 am

Caliche. We live in the desert, and there is no good earth here to be found. Everything has to be boxes with purchased dirt. 🙁

Jennifer Krieger February 25, 2011 at 11:20 am

I’m glad you didn’t take care of your problem. Good luck on finding alternate space.

Granola Girl February 25, 2011 at 2:25 pm

My husband. He’s a “yard” guy not a “food” guy.

Linda February 25, 2011 at 2:45 pm

I use raised beds. We also have a black walnut tree …I have been able to grow a few things under it but not much so I stopped. You know why.


Laura February 25, 2011 at 8:33 pm

I had no idea about the trees, and I am really surprised to find out about the sunflowers. I read they could be used for trellises for peas and such. So much for my “cheap” trellises…. Thanks for the good info.

alisha February 25, 2011 at 8:53 pm

For 6 yrs it was my neighbors trees next to us causing lots of shade, but he took them out last year just before planting. My garden LOVED the sun! 🙂

Lena in Maryland February 25, 2011 at 9:13 pm

Never heard about allelopathy with sunflowers, and looked it up. Unlike black walnuts — a very well researched problem — the effect of sunflowers next to seedlings isn’t well established. See for an interesting discussion that also involves the scale of the garden being planted and whether or not you’re growing from seed or putting in seedlings.

Thanks for an interesting entry! To answer your query, my biggest challenge is myself: especially at this time of year I’m dreaming of far more crops than I’ll be able to handle! (And I too do raised beds; soil here extremely clay-y.)

Lena in Maryland February 25, 2011 at 9:13 pm
Joy February 25, 2011 at 9:24 pm

I don’t have much yard that I could grow things in. I share a yard with my neighbors and a rabbit. I mostly container garden on my deck. I can’t wait to have a big garden someday, until then I will have to shop at the farmers market.

jan February 26, 2011 at 5:49 am

I learned something new here today. Now I know why I could never grow anything among my walnut trees in the front yard. I tried several types of flowers in beds there, and nothing survived, no matter how much I cared for them. Finally gave up on that. I have several small raised beds in the back yard that I use for vegetables, that do fine. Only a pear tree back there. Thanks for all your helpful information.

Coyote February 26, 2011 at 1:47 pm

WOW, I totally didn’t know that. I’ll have to keep that in mind. We were having a problem with the birds and squirrels “planting” sunflowers everywhere, so now we feed them roasted sunflowers and peanuts. Seemed to take care of that problem, 😉

Tanya Walton February 26, 2011 at 2:22 pm

I was going to suggest raised beds…you can have them on feet so they are actually above the ground and once lined they will be easily managed…maybe a little costly on the outlay but well worth it to keep two such beautiful trees and still grow your veggies!!

judy February 26, 2011 at 3:05 pm

My dogs share the same yard as my flower garden. They accept plants grown from seed but it is their firm resolve to remove all new plants. Even the seedlings suffer. I need to fence my beds from the dogs.

audrey February 27, 2011 at 9:44 am

Just took a permaculture class and they gave us some ideas of what we can do under walnuts. First suggestions was to plant mulberry bushes around the walnut. apparently the mulberry will neutralize the bad chemical that the walnut tree releases. Then intersperse gooseberry or currant bushes between the mulberry. And they say comfrey and mints will still grow under the walnut. Then you can add dwarf cherry trees on the outer rim.

Kathy February 27, 2011 at 12:14 pm

Black walnuts are a problem if you want to grown anything under them. Since they are so large, it’s easy to become annoyed by their presence. But please research the benefits of black walnut before chopping any down. My dh’s grandmother has them in her yard. Every year she steeps unhulled walnuts in spirits to make medicine. While I was visiting, it came in handy whenever my stomach was upset. Each morning after taking it I felt stronger and full of energy. Everything I found says it’s good for parasites, but it helped whenever I felt quesy late at night.

Kris Bordessa February 27, 2011 at 11:07 pm

I worked in a landscape architecture firm for years and we had several clients come through who wanted to landscape around former black walnut orchards. It was a difficult task, but we did learn a lot about what will grow with the juglone in the soil. These days, my biggest garden problem is the fruit flies that make growing tomatoes and zucchini (yes, ZUCCHINI!) hard to grow in this tropical climate.

dana February 28, 2011 at 11:25 am

my neighbor has the dreaded black walnut and after years of fighting it, i went with it. I made raised cinder block beds and am happy to report my herb garden (every kind of herb) has grown amazingly along with tons of different types of lettuce!!!!!!!! I also have a black raspberry patch with tons of eqyptian walking onions that are thriving.

Jessie February 28, 2011 at 2:36 pm

I had no idea about the walnuts – good to know! I was thinking of putting in a nut tree, now I know to look for one that plays well with others.

My biggest nemesis is the woodchuck. Or rather, woodchuck #3. One is forced out and another moves in and loves the buffet in my back yard.

Carmen March 2, 2011 at 2:00 pm

Do you have your raised beds near the black walnut trees or somewhere else? I was under the impression that any where the nuts could fall would be a bad place for a garden. Our back yard is full of black walnut trees. For the most part I hate them – they are the last tree to get their leaves in the spring and the first to lose them in the fall. We finally found a place in our side yard where I could have a few square foot gardens.

Tomato Lady March 2, 2011 at 4:27 pm

Carmen–The raised beds are near, but not directly under the trees, so I can keep the leaves and fruit out of the beds themselves. As far as shade is concerned, the early/late leaf issue is a plus near the garden, but, yeah, other than plain old tree beauty, they are not friendly things for me as a gardener. Glad you found a space for your raised beds.

sondra March 5, 2011 at 7:21 am

I didn’t know that about sunflowers. My brother-in-law borders his veggie garden with them everyyear and has always had a gorgeous, bountiful garden. Thanks for the info about the trees too, is that just black walnut or all walnut trees that do that? We have nuts from our old house that we were wanting to plant at our new place. I can’t remember what kind they are though but I do know that they are not black walnut.

Tomato Lady March 5, 2011 at 10:22 am

sondra–I think all walnut trees (and related nut trees) have lesser amounts of juglone, but that it has a very limited or no effect on soil toxicity. So you’re in the clear.

ANny March 6, 2011 at 7:21 pm

I also have a huge black wallnut tree in my yard, what have you found grows will near it?

steve March 15, 2011 at 9:05 am

Any way to neutralize walnut saw dust mistakenly placed in a vegetable garden? Or is it really a problem?

Tomato Lady March 15, 2011 at 12:15 pm

steve–This is a pretty comprehensive overview. As you will read, some believe black walnut sawdust doesn’t contain juglone, others disagree. I found it interesting that nitrogen is considered to neutralize the effects, and would like to learn more about that. For the organic gardener with black walnut trees, that might mean stocking up on blood meal. Letting the sawdust compost seems to be widely accepted by the experts. It’s likely going to depend on many factors, including how much of that sawdust is in your soil, how long it’s been there, and the sensitivity of those plants to juglone toxicity. Plant squash, melons, beans or corn, etc., to be on the safe side!

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