As a northern fruit gardener, if you’ve managed to get your fruit trees and plants to survive subzero winters, you’re doing great – but you aren’t out of the woods yet. Your fruit garden still needs the right water, soil, and environmental characteristics to survive… 

…and for many fruit trees, the biggest threat to survival comes from nearby nut trees.

If you’ve never heard of the chemical compound “juglone,” it’s time to prepare against this incredibly damaging risk to your fruit trees and plants.

What is Juglone?

Juglone is a chemical compound that is naturally emitted by any type of organic material from juglone-producing trees.

Fallen leaves? Check. The juglone leaches out of those decaying leaves, right into the soil.

Underground roots? Double-check! And even if the tree is DEAD, those roots continue to emit juglone into the soil as they decompose!

Shells and husks of fallen nuts? Woodchips or sawdust from removed or trimmed trees? Fallen branches? Check, check, and double-check.  Any organic material from a juglone-producing tree – from roots to foliage – will leach juglone into your soil.

Juglone is completely compatible with certain trees and plants, but for many plants – particularly fruit trees – it is highly toxic. Juglone is such an effective plant killed that it is often used in herbicides. 

Bonus points: Juglone is also toxic to animals as well. Don’t EVER use black walnut shavings in a horse stall!

What Trees Produce Juglone?

One of the biggest producers of juglone is the black walnut tree, but it’s not the only offender on the scene! The toxin is produced by any tree in the walnut family (which so happens to be named the “juglandaceae” family… and now we know why).

Not familiar with other members of this group?

In addition to the black walnut tree, other juglone producers include the butternut tree; the English walnut tree; the hickory tree; and the pecan tree.

Obviously, the pecan tree is less of a concern for northern growers because it’s unlikely to survive north of zone 4, but also be aware: different members of this family produce different amounts of juglone. Some are far more potent than others.

Of the entire group, the black walnut tree is one of the worst offenders, so that tree should be your biggest concern.

What Fruit Trees and Plants Are Tolerant of Juglone?

Fortunately, there are some fruit trees and bushes that are able to tolerate juglone in the soil. Please note this is not an exhaustive list!

Please note that just even if a fruit is listed as “tolerant” of juglone, that doesn’t mean it’s safe! Tolerance might mean “immune,” but it might also mean, “might not die, but won’t produce fruit if exposed, either.” 

I can’t say this enough: Never underestimate the chance of losing even “tolerant” plants to juglone toxicity. Even tough plants can be weakened enough to fall prey, and a small dose of toxin is very different from a highly-concentrated, constant exposure to it. Plant wisely, and take steps to reduce exposure whenever possible.

• Serviceberry: Also known as the saskatoon blueberry or juneberry, the service berry is native to many of the same geographic areas as the black walnut tree, and is generally pretty tolerant of juglone. I see this combination in action in the woods all around my house!
• Pawpaw: Full disclosure? At the time of this posting, I’ve never grown a pawpaw. However, this tree is listed as juglone-tolerant by Penn State University’s post on gardening around juglone-producing plants. Again, this is a native fruit that hails from the same geographies as heavy juglone producers, so it’s got an extra leg up on the competition.
• Elderberry: I love my elderberry plants. They’re tough, useful, and easy to grow… and more juglone tolerant than many other fruits, too! Do be careful to make sure you aren’t confusing elderberries with pokeberries (pokeberries are highly toxic!), and be aware that elderberries are slightly toxic when underripe!
• Black raspberry: These guys are like the invincibles of the fruit gardening world. They survived – and thrived! – in a juglone-SATURATED portion of the property. I’m talking a section where apple trees died and even strawberries (which are supposedly mildly juglone-tolerant) died by the hundreds. But the black raspberries? Reproducing and fruiting like crazy! Read more about different types of raspberries.
• Currant: The Ribes family is tough to kill! Currants have decent juglone toxicity, but beware; many locations around the US have a ban on growing Ribes because the family was once thought to be a major host for white pine blister rust.
• Cherry: My cherry trees are all far enough from my black walnuts that I can’t say I’ve personally tested the combination, but Penn State lists the “Prunus” group as juglone-tolerant. This is a good thing, because that includes the Cherry and its many fruity cousins! (Just make sure you select a sweet cherry cultivar that will survive zone four and colder, and take some time each fall to winterize your cherry trees correctly, because all the juglone-tolerance in the world won’t help your tender fruit trees survive frigid temperatures.)
• Nectarine: Like the cherry, the Nectarine is a “Prunus” member, so you have some good juglone tolerance built into the tree’s genetics. Finding a zone-4 hardy nectarine might be your biggest barrier if you are a northern gardener!
• Plum: I grow several different types of plums, and they are right on the border of my property… which is awfully close to the danger zone for the neighbor’s wild black walnut trees. Because plums are a juglone-tolerant prunus member, they are less of a concern than my apple trees. (As with anything, careful is always better… but there’s a better chance of success with plums than with some of the more sensitive fruits).
• Peach: Once again, a prunus, so the juglone tolerance should be reasonable. Northern gardeners might struggle finding peach trees cold-hardy to zone 4, though, so you might wat to consider killing two birds with one stone, beating the cold and the juglone danger by growing “bush” peach trees in pots.
• Quince: Sadly, I don’t grow this cold-hardy, unusual tree fruit (yet). However, if you are looking to add the quince to your orchard, heads up –  it is reportedly tolerant of juglone-producing neighbors. If I ever add it to the property, I’ll update the post on its hardiness!
• “Wild” grapes: What’s a “wild” grape? I’m not really sure. All of my seedless grapes are planted FAR away from juglone-producing species, just in case… but according to the University of Wisconsin, wild grapes are considered to be juglone-tolerant. Does this mean my seeded Concords are OK with black walnuts? I don’t know, and I’m not about to test it. My rule of thumb is if in doubt – don’t!
• Walnut-Family Nuts: OK, this should be self-evident, but since juglone is produced by the walnut family, these nut trees should be tolerant of it! Think walnuts (black and English), hickories, pecans, and butternuts. I’ve heard the hazelnut is tolerant also, but I haven’t personally tested it. Not all of these nut trees are rated to survive in zone 4 and colder, but just FYI!

What Fruit Trees and Plants are NOT Tolerant of Juglone?

This is of course a VERY limited list, but some of the most vulnerable fruits when it comes to juglone tolerance.

• Apple: Personal experience here, folks. Apple trees are total wimps when it comes to juglone. I’ve seen a gorgeous apple stand reduced to husks of rotting tree trunks in just a few short years when a black walnut sprang up in the middle of the orchard. What a crying shame. Don’t risk it; apples are absolutely incapable of fighting back when there’s juglone toxicity in the soil.
• Blackberry: I haven’t planted blackberries under walnut trees (because, duh), but I’ve noticed the natural selection around juglone-heavy soils. Black raspberries? Sure. But the wild blackberries that are so prevalent everywhere else around my property don’t seem to creep in under the walnut trees. (And if you don’t trust my anecdotal advice, FYI the University of Wisconsin drops the blackberry under its juglone-sensitive category.)
• Blueberry: As if growing blueberries didn’t come with enough soil problems already, juglone is on its no-go list. (Tired of fighting soil acidity problems with the blueberry? Consider switching to growing honeyberries, also commonly called haskaps or yezberries. Worth a look!)
• Pear: Pears are another susceptible fruit tree when it comes to juglone soil toxicity. Buyer beware!
• Strawberries: OK, I don’t care what you’ve read online. Strawberries are NOT happy when there’s juglone in the soil. I planted them in the danger zone because I found an internet article that listed them as “tolerant.” However, after the entire bed died, I went back and researched a little more heavily… and found out that although strawberries are slightly more juglone-tolerant that some other berries, they still can’t handle heavy concentrations in the soil. Don’t risk it. You’ll regret it!

Other Learning Resources on Juglone

Most or all of the plants listed above have been confirmed as juglone-tolerant or sensitive by multiple state extension offices (University of Wisconsin and Penn State are two examples), but it never hurts to get another opinion, so reach out to your local extension office to find out what these experts recommend!

Trying to limit juglone toxicity but not sure what nut trees other than black walnuts will work in your zone? Check out my article on nut trees cold-hardy to zones 4 and colder.