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Black walnut trees are notoriously picky when it comes to companion planting. These beautiful trees may be a magnificent sight, but they also secrete a substance called juglone that is highly toxic to a huge number of other plant species. If you’re struggling to get any plants to thrive near a black walnut tree, this is probably why.

But the good news is that some plants grow very happily near black walnut trees, seemingly immune to the toxic effects of juglone. To help you plan what to grow in and around these wonderful trees, we’ve found 15 of the very best companion plants for black walnuts.

1. Narcissus

Dutch spring, colorful yellow daffodils flowers in blossom on farm fields in april near Lisse, North Holland, the Netherlands
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A sea of narcissus flowers is a beautiful sight in early spring, and these bulbs will put on a showy display when planted under the canopy of black walnut trees. Other flowering bulbs that are tolerant to juglone include grape hyacinth, tulip, and hyacinth.

2. Onions

Close-up of growing green onion in the vegetable garden.
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If black walnut trees grow adjacent to your vegetable plot, finding crops that will thrive in this location can be tricky. Onions and other alliums, such as leeks and garlic, are unaffected by juglone and can be planted around the periphery of a black walnut tree canopy.

3. Persimmon

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Persimmon trees make the ideal partner for black walnut trees in a food forest or orchard. As persimmon saplings can grow into a substantial sized tree, make sure to space them at least thirty feet apart.

4. Violets

wild violet
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Violets thrive in damp, shady locations, making them ideal for growing under the leafy canopy of black walnut trees. This low-growing plant is great for quickly covering bare patches of ground, rewarding you with a beautiful display of pale purple blooms throughout the spring.

5. Pot Marigold

Flower with leaves Calendula (Calendula officinalis, pot marigold, garden or English marigold) on blurred green background. Note: Shallow depth of field
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Pot marigolds, also known as calendula, create a bold splash of color that contrasts perfectly with black walnut trees. These flowering plants are one of the best options for attracting beneficial insects that help boost pollination and reduce pests in both ornamental and vegetable gardens.

6. Squash

Vegetables (winter squash Crown Prince) growing in a raised bed in a UK garden in summer.
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It can be difficult to find space to grow a lot of squashes, as these sprawling plants take up a huge amount of room. So, if you’ve got an area under black walnut trees where nothing grows, try placing a few squash plants nearby to take advantage of the extra space.

7. Bee Balm

Tall red flowers of Monard bee balm in the summer garden
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Bee balm is a woodland plant that thrives in shaded locations such as under black walnut trees. These perennial plants put on a fine display of daisy-like flowers on tall stems that attract bees, butterflies, and hummingbirds to your garden.

8. Peony

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Peonies are low-maintenance flowering perennials that produce an abundance of showy blooms on a background of lush evergreen foliage. These plants enjoy plenty of sun, so plant them on the south edge of the walnut tree canopy for best results. 

9. Cherry

cherries cherry tree
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Cherry trees will grow happily alongside black walnuts, giving you another option for a fruit orchard or food forest. If you have limited space, cherry trees grafted onto dwarf rootstock can be planted closer together.

10. Soloman’s Seal

Soloman’s Seal
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Soloman’s seal is a beautiful woodland plant that produces a sea of delicate white blooms above a mass of dense green foliage. This plant grows best in a shaded damp location, making it the ideal partner for black walnut trees.

11. Crabapple

crab apple crabapple
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Crabapples are medium-sized ornamental trees that produce small fruits that are perfect for making preserves. They are prized for their prolific blossoms in spring that attract a whole host of pollinating insects.

12. Corn

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Most grasses, including corn, are unaffected by the toxins secreted by black walnut trees. Plant rows of corn near to the edge of the tree canopy where they will get plenty of sun.

13. Hawthorn

hawthorne berries
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Hawthorn is commonly grown along boundaries to form a hedgerow, as its dense, spiky growth habit is ideal for keeping animals such as deer at bay. Hawthorn berries are a prized food source for wildlife during the winter months.

14. Crocus

crocus purple flowers
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Dainty crocus flowers have no issues growing under black walnut trees, forming a carpet of pretty blooms during late winter and early spring. Crocus bulbs will rot in damp grounds, so pick a spot with well-drained soil.

15. Viburnum

Viburnum × burkwoodii in Hilltop Garden at RHS Garden Hyde Hall, Essex, England
Image Credit: Acabashi, CC BY-SA 4.0 via Wikimedia Commons

Viburnums are not particularly fussy about where they grow and can be cultivated successfully around black walnut trees. This flowering shrub is ideal for ornamental gardens, producing a display of beautiful blooms in a variety of colors.

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