Best Juglone-Tolerant Plants for Food Gardens Near Black Walnut Trees

By Steven Biggs

Growing Food Crops Near Black Walnut Trees

I bought my current home in the late winter when there were no leaves on the trees. So I didn't notice that the massive black walnut tree next door. Yikes! It's created a lot of gardening hurdles.

Black walnuts are known for their beautiful wood. Prized in fine woodworking. But there's a sinister side too...they have the odious reputation as trees that poison nearby plants.

A commercial grower or a gardener in a rural area might react with a chainsaw. Not an option for most home gardeners. Especially in the city where trees have the same rights as taxpayers.

But I've figured out how to grow a thriving vegetable garden, edible landscape, and fruit crops all around that black walnut tree. If you want to grow food crops alongside these beautiful but challenging trees, keep reading: This post tells you what you need to know to successfully grow food plants—even if your yard is overshadowed by a black walnut tree.

Primer: Black Waltnut Toxicity

• Black walnut (Juglans nigra) trees give off something called juglone, which can affect the growth of nearby plants. Not a bad thing from the walnut's perspective...because there's less competition.

• Juglone is in all parts of the black walnut tree, including the roots, leaves, and the nuts.

• Not all plants are affected by juglone.

• As juglone builds up in the soil under and around the tree, it affects nearby susceptible plants.

• If you like the technical lingo: When a plant makes something that inhibits the growth of other plants, it's called "allelopathy."

Tips for Gardening Near Black Walnut Trees

Sources of Black Walnut Toxicity

Let's take a look at how juglone gets from the tree into your soil. If there's a walnut tree, you'll have more juglone than you want. But you can do some things to reduce black walnut toxicity in your garden.

Black walnut hulls also contain juglone.

• Roots. Walnut tree roots release juglone into the soil. Remember the black walnut roots if you're thinking of raised-bed gardening, because tree roots can (and do!) grow up into raised beds. You need a raised bed that the roots can't get into. (See below, Raised Beds.)

• Leaves. I don't bother removing walnut leaves from my vegetable garden beds near the black walnut tree. Those beds are already loaded with juglone. But I do remove fallen walnut leaves from my raised beds, where the soil is not contaminated with juglone. I don't compost black walnut leaves with leaves from other parts of my yard. No point making killer compost. (Composting breaks down juglone, but in a home garden we don't have perfect composting conditions, so you won't know how long until your compost is juglone-free.)

• Nuts. Black walnut hulls also contain juglone. Again, I removed them from the raised beds where the soil isn't full of juglone. If I'm not fast, the squirrels help with cleanup! Bothered by squirrels? Here are 50 ways to foil squirrels in your food garden.

• Wood. If you're getting a load of wood chips from an arborist, make sure there isn't chipped black walnut in there!

Other trees in the same family as black walnut (the Juglandaceae family) give off juglone too. These include butternut, pecan, English walnut, heartnut, and hickory. But black walnut gives off the most, hence its reputation and the term "black walnut toxicity."

How Big is the Walnut "Kill Zone"

The bigger the tree, the bigger the zone where you’ll get black walnut toxicity. My neighbour’s tree is big…and so is the kill zone.

I remember hiking in a nearby ravine with a semi-wooded, scrubby area. The scrub was dotted with young black walnut trees. And underneath these young trees there was mostly grass. Like a doughnut under each tree. Far less competition. I call that the "kill zone."

The size of this kill zone in your yard depends on how big the tree is and how well drained the soil is. Soil drainage, soil type, and microbes are involved in breaking down juglone. That just means that determining the size of the kill zone is not an exact science.

When I first started gardening near my neighbour's big black walnut tree, I figured that if I planted beyond the "drip line" (which is what's under the tree canopy) it might be OK.

It wasn't.

The young espaliered apple trees I'd worked hard to shape? Toast. Even though they were 15 metres away. The effects of juglone can extend well beyond the drip line of big trees. For a big tree, I'd use 15 metres as a starting point. The farther the better.

Symptoms of Juglone Toxicity

Juglone can cause yellowing leaves, partial or total wilting, stunted growth, and, possibly, death of susceptible plants.

The symptoms might look like drought stress at first. That's what I saw the first time it affected our tomato crop: Wilting even when there was ample soil moisture. But by then, it's too late. Game over. No matter how much you water.

Walnut-Wise Food Gardening

3 Steps to Create a Thriving Vegetable Garden or Edible Landscape Near a Black Walnut Tree

1. Consider the kill zone. Once you've mapped out the likely kill zone, you can start planning where to put your juglone-sensitive plants, and where to put your juglone-tolerant plant species. Play it safe, and assume the kill zone is bigger rather than smaller.

2. Choose wisely. There are oodles of plants that are tolerant to juglone. Use the lists below to help you choose what to grow—and what not to grow.

3. Keep crops out of affected soil. Use containers and raised bed to grow juglone-sensitive plants close to a black walnut tree. But you have to do it right. (But see Raised Beds, below, so that you do it right.)

Underneath my neighbour's black walnut tree I have a small pawpaw patch (these are shade-tolerant native plants with a really tasty fruit, worthwhile working into your walnut-wise garden.) There's also small fruit such as bush cherries, chokeberry, and autumn olive closer to the edge of the dripline, where there's more sunlight. Then, further out, where there's a bit more sun, I have raised beds for juglone-sensitive plants. And finally, still within the kill zone, I have a really big veg patch, filled with crops that aren't affected by juglone.

Container Veg Gardening Course

As well as helping with your walnut problem, a container garden is a great way to harvest more from a small space. If you want to take container gardening to the next level, check out the course below on vegetable container gardening.

Raised Beds and Containers to Solve Black Walnut Toxicity

A raised bed allows you to grow juglone-sensitive crops in the kill zone. But you have to set it up properly...or it won't help for long. Tree roots grow up into raised beds.

This is a wicking bed, very close to a black walnut tree (see the tree trunk in the back corner of the photo.) A wicking bed is one way to grow juglone-sensitive plants near a black walnut tree.

Failure 1. My first attempt at growing tomatoes in the ground near the tree failed. To be expected. So I reasoned that if I made a simple wooden raised bed, lined the bottom with landscape fabric, and added uncontaminated soil, it would solve the problem. At first, it seemed to work. But by mid summer, the tomatoes wilted badly. The reason? The roll of fabric wasn't as wide as the bed. And even though I overlapped the fabric so that the "new" soil above was separated from the contaminated soil below, tomato roots could find their way into the soil below...and walnut roots could grow up into the raised bed.

Failure 2. Another year I tried strawbale gardening. I reasoned that I could grow tomato plants in bales, near the walnut tree, if I put down a layer of plastic mulch under that bale to keep the tomato roots out of the soil below. This might have worked...except I used a biodegradeable plastic mulch, and part way through the season those tomato roots made the journey to juglone hell. Game over. (But strawbale gardening is an excellent technique. Find out how to use strawbales to create awesome food gardens.)

Success! I realized that tree roots quickly grow where they're not wanted...and the same goes for tomato roots. So I needed a bed that isolated the tomato roots. The answer was something called a "wicking bed." In short, it's a bed that has a thick liner at the bottom, creating a reservoir. They're usually used in dry areas, as a way to conserve water...but they fit the bill perfectly. Here's more information about using wicking beds.

On a smaller scale than a raised bed such as a wicking bed, container gardening is another way to grow sensitive plants near a black walnut tree. I'm a big fan of sub-irrigated planters (a.k.a. SIPS), which, like wicking beds, cut back on how often you need to water. Here's more about SIPS.

Plant Lists for Walnut-Wise Food Gardens

Here are edible plant lists you can use to plan your walnut-wise garden. These are from my experience and from published sources such as extension agencies and universities. Sometimes recommendations by published sources differ, so consider this a guide—not cast in stone.

Juglone-Sensitive Plants

Sensitive Plants - Fruit Trees and Shrubs

• Apple

• Crabapple

• Blackberry

• Blueberry

Sensitive Plants - Vegetables

Peppers and other plants in the nightshade family are sensitive to juglone.

Wondering what vegetables are sensitive to juglone? Plants in the nightshade family (Solanaceae) practically wilt at the mention of juglone. This family includes lots of the must-grow veg crops such as tomatoes, peppers, potatoes—but also some less common ones such as cape gooseberry and ground cherry.

• Asparagus

• Cabbage and family

• Eggplant

• Pepper

• Potato

• Rhubarb

• Tomato

Plants Tolerant to Juglone

Wondering what grows well near a black walnut tree? Many plants grow just fine under or near a walnut tree. So if you're wondering how far should a garden be from a black walnut tree, you can garden quite close to the tree if you choose juglone-tolerant plants and take into account the shade. Here are key edible plants to get you started.

Juglone-Tolerant Plants - Fruit Trees and Shrubs

Saskatoon is an example of a fruit bush that is not juglone-sensitive.

Wondering what fruit trees are juglone tolerant? You have a lot of choice!

• Autumn Olive (loved by foragers, though disliked by some because it can be an invasive here in Southern Ontario)

• Cherry, Peach, Plum, Nectarine (fruit trees and bushes in the Prunus clan, what people often call stone fruit)

• Chokeberry

• Currant and Gooseberry

• Elderberry

• Figs

• Grape

• Hazelnut

• Mulberry

• Pawpaw

• Black raspberry

• Serviceberry (including saskatoon, a.k.a. juneberry)

Here are 5 types of bush cherries you can grow.

Find out how to grow saskatoons.

Juglone-Tolerant Vegetable Crops and Herb Crops

Wondering what vegetables and herbs will tolerate juglone? There are many vegetables that tolerate juglone, so you have quite a few options.

Here’s a corner of the veg patch I have near the black walnut tree, where I grow carrots, beets, parsley, basil, squash, and corn very close to a large black walnut tree.

• Artichoke

• Basil

• Bean

• Beet

• Cardoon

• Carrot

• Chive

• Corn

• Cucumber

• Dill

• Edamame (which is soybeans while they're still green)

• Garlic

• Leek

• Melon

• Onion

• Parsley

• Parsnip

• Pea

• Squash

• Swiss chard

Other Walnut-Tolerant Edible Plants

• Bee Balm (edible petals)

• Dandelion (sure some people think of this as a weed, but great for early greens in the spring!)

• Daylily (edible flower buds, here's more on edible flowers)

• Grains such as wheat, millet, and sorgum

• Hawthorn

• Hosta (edible leaf spears in the spring!)

• Jerusalem artichoke

• Mint

• Nasturtium

• Pin cherry and choke cherry

• Redbud tree (edible flower buds)

• Rose (edible petals, rosehips)

• Staghorn sumac

Looking for edible flower ideas? Check out this list of edible flowers for home gardens.

Landscape with Fruit Course

It the above list of juglone-tolerant fruit has you thinking of planting fruit near your black walnut tree, here’s a course all about how to grow fruit in home gardens.

How to Use Black Walnuts - Yes, You Can Eat Them!

Black walnuts with husks removed.

While you're not likely to find black walnuts for sale, they are quite edible. Like other nuts, remove the hull and then air dry the nuts.

Note: The husk stain. I learned the hard way one year when my hands were a few shades darker for a week after hulling black walnuts. Someone later told me that a good way to get off the hulls is to pile the nuts until the hulls soften, and then send in kids dressed in old clothes and rubber boots to jump on the pile. I haven't tried it myself, but sounds as if it would work!

The challenge with black walnuts is cracking the shell. They're much more difficult to open than an English walnut. There is a vice-like device for cracking them open. I use a hammer. Or, I've heard of people driving over the nuts!

Key Takeaways

Pin this post!

• Black walnut trees give off a chemical called juglone, which affects some plants. This is sometimes called black walnut toxicity.

• This doesn't mean that you can't garden hear a black walnut tree—but that you need to choose tolerant plants and use raised beds or containers.

• The size of the affected area around a tree depends on its age, the soil type, and soil moisture.

FAQ

Can I just cut down my black walnut tree to solve the problem?

Sorry...that would still leave lots of roots all through the soil, and, therefore, lots of juglone. Because it can take a few years for all the roots to decay, it's not a quick fix. In short, juglone can persist for a few years after a black walnut tree is removed.

How far should a garden be from a black walnut tree?

For a mature tree, the kill zone extends beyond the tree canopy and can be more than 15 metres from the trunk.

Find This Helpful?

Enjoy not being bombarded by annoying ads?

Appreciate the absence of junky affiliate links for products you don’t need?

It’s because we’re reader supported.

If we’ve helped in your food-gardening journey, we’re glad of support. You can high-five us below. Any amount welcome!

$10.00

$20.00

$30.00

$40.00

Custom Amount

Please enter an amount

$

High Five! High Five!

Food Gardening Articles

Edible Landscaping

Exotic Edibles

Figs

Fruit

Herbs

Vegetables

Food Gardening Courses

Find out how to grow more great food at home with our online courses. We have both live and self-paced courses.