Plenty of plants grow just fine under a black walnut tree — you just have to pick from the right list! Black walnut produces a compound called juglone that some plants can’t tolerate, but many trees, shrubs, and perennials handle it without any trouble at all.
Why black walnut is tough on some plants
If you’ve got a black walnut somewhere in the yard, you’ve probably already noticed something’s off in your gardening journey–that’s why you’re here looking for answers. Maybe its a patch of tomatoes that never quite thrives like it should, a peony that struggles no matter how much you baby it, azaleas that just refuse to take off. You’ve been thinking it’s the sun, your watering schedule, the wrong fertilizer, or the soil pH. You’ve tried everything you can think of, but in reality it’s just the nearby tree that’s the culprit. What you need are some black walnut tolerant plants!
Black walnut is a genuinely great tree — strong, long-lived, valuable for lumber, and one of the true native hardwoods that can anchor a big landscape for generations. But it also does something most other trees in your yard don’t: it defends its territory chemically. The tree produces a compound called juglone in its roots, leaves, husks, and bark. As those parts break down, juglone builds up in the soil beneath and around the canopy, and certain plants just can’t handle it. They’ll yellow, wilt, or stall out no matter what else you do for them.
This kind of chemical standoff between plants has a name — allelopathy — and black walnut is one of the best-known examples of it in home landscapes. Worth noting: the science here isn’t as buttoned-up as you’d think. Most of what we know traces back to a single study from decades ago, so treat any “tolerant” or “sensitive” list, including ours, as a solid starting point rather than gospel.
A few black walnut gardening tips
Keep the most sensitive plants out of the root zone entirely — that’s roughly the same footprint as the canopy, sometimes a bit wider on a mature tree. If you want to garden nearby, a raised bed will help, but don’t let the leaves, twigs, or walnuts fall into or drift into the soil, though. And skip walnut bark or wood chips as mulch anywhere near plants you care about — juglone travels into the soil right along with them.
Black walnut tolerant plants that actually thrive
The easiest fix when gardening near black walnuts is just picking plants that tolerate the jugalone from the black walnut. There’s a longer list than most people expect — hostas, ferns, redbud, viburnum, elderberry, and plenty of perennials–including many native plants–all do just fine growing right in that root zone.
Grasses hold up well too. Little bluestem, switchgrass, and prairie dropseed are all juglone tolerant and reliably hardy through zone 4b, so they’re a solid choice if you want movement and winter texture near the tree without the risk. And if you’re leaning toward native plants, purple coneflower, black-eyed Susan, goldenrod, and Joe-Pye are straight Minnesota natives that shrug off juglone without any fuss — a nice way to support pollinators in a spot where a lot of other plants won’t cooperate–as long as there is adequate sun of course!
We put together a full list of black walnut tolerant plants organized by category — trees, shrubs, perennials, evergreens, and vines — that you can grab as a PDF, or stop in and we’ll walk through it with you in person.