Thriving Beneath Black Walnuts

Black walnut trees (Juglans nigra) are stunning landscape features - tall, stately, and generally, a low-maintenance tree. There’s just one catch: their roots release a natural compound called juglone that can stunt or kill many common landscape plants. The good news? Plenty of gorgeous, shade-loving perennials shrug off juglone like it’s nothing.

If you’ve got a black walnut in your yard and have been hesitant to plant underneath it, here are five proven winners that our landscaping team have found to grow beautifully under black walnut trees.

1. Asters

For late-season color when everything else is winding down, plant asters around the sunnier edges of your walnut’s drip line. These fall-blooming beauties come in jewel-tone purples, pinks, blues, and whites and show no ill effects from juglone exposure.

• Height & Spread: 1–6 ft tall × about 2 ft wide (variety dependent)
• Best Conditions: Full sun to light shade; average, well-drained soil
• Top Choices: New England aster (Symphyotrichum novae-angliae) and aromatic aster (Symphyotrichum oblongifolium) are butterfly magnets.

  Large patch of aster flowers. | Harlan B. Herbert, Bugwood.org

2. Blue Flag Iris (Iris versicolor)

Nothing signals the arrival of late spring quite like the striking violet-blue blooms of blue flag iris. Accented with bold yellow markings, these natives love the same moist conditions that black walnuts prefer and happily accept the dappled shade beneath the canopy.

• Height & Spread: 2–3 ft tall × 2–3 ft wide
• Best Conditions: Full sun to part shade; consistently moist to wet soil
• Bonus: Long-lasting flowers and sword-like foliage that looks sharp all season.

  Close up of blueflag iris flower. | Rob Routledge, Sault College, Bugwood.org

 3. Ferns

Want lush, feathery texture without worrying about juglone? Ferns are practically bulletproof under black walnuts. Christmas ferns, ostrich ferns, and autumn ferns have all thrived for us in these challenging spots, adding year-round (or late-into-fall) greenery.

• Height & Spread: Varies by species—6 in to 4+ ft
• Best Conditions: Part to full shade; moist, well-drained soil
• Favorite Pick: The native Christmas fern (Polystichum acrostichoides) stays evergreen even in tough conditions.

 Mature Christmas fern plant. | Rebekah D. Wallace, Univ. of GA, Bugwood.org

4. Hostas

When it comes to shade-tolerant, juglone-resistant foliage plants, hostas are the undisputed champions. With hundreds of varieties offering everything from tiny leaves to dinner-plate-sized giants - and colors ranging from chartreuse to deep blue-green - there’s a hosta for every spot under your walnut tree.

• Height & Spread: 4–36 in tall × 6–60 in wide (variety dependent)
• Best Conditions: Part to full shade; rich, well-drained soil
• Pro Tip: Slug-resistant varieties like ‘Halcyon’ or ‘June’ tend to hold up especially well when competing with tree roots.

 Hosta plant in flower. | John Ruter, Univ. of GA, Bugwood.org

5. Jack-in-the-Pulpit (Arisaema triphyllum)

Looking for something a little unusual? Jack-in-the-pulpit is a woodland gem that never fails to spark conversation. Its hooded, preacher-like flower (the “Jack” standing in his green “pulpit”) is followed by brilliant red berries in fall. This native plant loves shade and moisture and couldn’t care less about juglone.

• Height & Spread: 1–2 ft tall × 1–2 ft wide
• Best Conditions: Part to full shade; rich, moist, well-drained soil (avoid heavy clay)
• Fun Fact: It goes dormant by midsummer, making it a perfect companion for spring bulbs or later-emerging perennials.

                                         Jack-in-the-pulpit plants. | Richard Gardner, Bugwood.org

Quick Tips for Success Under Black Walnuts

• Plant a little higher than normal - the roots compete fiercely for water.
• Add plenty of organic matter when planting to help new plants establish.
• Water deeply but less frequently to encourage roots to grow down, away from surface juglone concentrations.
• Mulch well (but keep it a few inches away from trunks and crowns) to retain moisture and suppress competing grass.

With these juglone-tolerant beauties, that tricky shade under your black walnut can go from barren to breathtaking. Ready to transform the area under your black walnut tree? Give us a call - we’d love to plant the perfect combinations for your yard!