10 Plants to Grow Under Black Walnut

Do you have a Black Walnut tree in your yard? Black walnuts are known for being tricky to plant under—but fear not, many native plants are used to sharing space with Black Walnuts and are a good pick for your garden.  

Black Walnuts Have a Rap for Being Bad Neighbors

Black walnuts produce a chemical called juglone, which is present in all parts of the tree, including the roots, leaves, and nuts. When nut hulls, leaves, and stems fall to the ground, they leach juglone into the soil under and around the tree. Other trees in the Walnut family (Juglandaceae), like shagbark hickory, pecan, and English walnut, also produce juglone but in much lower concentrations.  

Because of these chemicals, certain plants won’t fare so well under or next to a black walnut tree. In fact, black walnuts are said to be “allelopathic” to their neighbors—a relationship in which one plant inhibits the growth of another plant by releasing toxins. Know that vegetables in the nightshade family (like tomatoes, peppers, potatoes and eggplants), many annual flowers, and some trees and shrubs won’t do well with black walnut as their neighbor. Plant these kinds of vegetables and flowers away from your black walnut tree and out of its root zone. Also, keep these garden beds free of walnut leaves, twigs, and hulls.  

Black walnut tree at McDonald Farm
Black Walnut tree (right) at McDonald Farm

The Best Native Plants to Grow Near Black Walnut Trees

Fortunately, there are many native plants that share a habitat with black walnut trees and are adapted to tolerate juglone. Consider planting the following 10 native plants near your black walnut tree: 

1. Wild Ginger

A group of wild ginger plants

Asarum canadense

Wild ginger makes a great native groundcover, especially under trees like black walnut. 

Learn more about Wild Ginger 

2 Virginia Bluebells

Mertensia virginica 

Enjoy nodding clusters of blue flowers under your black walnut. Virginia Bluebells fade away after spring, so consider interplanting with later blooming flowers or plants with long-lasting foliage.  

Learn more about Virginia Bluebells 

3. Mayapple

Podophyllum peltatum 

Mayapples are umbrella-like spring ephemerals that can grow into dense colonies in the woodlands.  

Learn more about Mayapple 

4. Blue Flag Iris

Blue flag iris flower
John Munt, CC BY-NC 2.0, via Flickr

Iris versicolor 

If your black walnut tree is planted in a wet area or near a pond, blue flag iris can be a great choice. 

Learn more about Blue Flag Iris 

5. Jack-in-the-Pulpit

Philip Bouchard, CC BY-NC-ND 2.0, via Flickr

Arisaema triphyllum 

Add a touch of whimsy to your spring garden with Jack-in-the-Pulpit. Mature plants produce clusters of bright red berries in the fall.  

Learn more about Jack-in-the-Pulpit 

6. Pennsylvania Sedge

tufts of sedges
Susan Harris, CC BY 2.0 via, Flickr

Carex pensylvanica 

Tufts of sedges look lovely under trees. Look closely for its flower clusters in the spring.  

Learn more about Pennsylvania Sedge 

7. Wild Geranium

wild geraniums picture

Geranium maculatum 

Wild geraniums can be grown as a groundcover with attractive pink-purple flowers. Wild geraniums bloom in late spring.  

Learn more about Wild Geranium 

8. Great Blue Lobelia

Great blue lobelia flowers
Andrew C, CC BY 2.0, via Wikimedia Commons

Lobelia siphilitica 

Spike-like racemes of blue-purple flowers make great blue lobelia a unique and showy native flower. Great blue lobelia blooms in late summer or fall.  

Learn more about Great Blue Lobelia 

9. Ostrich Fern

A few ostrich fern plants
harum.koh, CC BY-SA 2.0, via Wikimedia Commons

Matteuccia struthiopteris 

Add lushness to your understory with ostrich ferns and other native ferns.  

Learn more about Ostrich Fern 

10. New England Aster

Symphyotrichum novae-angliae 

Many asters are juglone-tolerant. Add a pop of purple in the fall with New England aster. 

Learn more about New England Aster 

Pick the Right Plant Companions for Your Black Walnut Tree

A successful native plant garden starts with finding the right plant for the conditions of your garden site. Choose native plants, like those listed above, that naturally share a habitat with black walnuts and are tolerant to juglone. Consider a combination of native flowers with different bloom times so you’ll have color and feed pollinators from spring to fall.  

For more information on black walnut toxicity and juglone-tolerant plant recommendations, check out these resources from The Morton Arboretum and Prairie Moon Nursery.  

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