What kinds of plants should I grow beneath black walnut trees? We at Greenwood Nursery get this question pretty frequently. It’s a valid question, as not all plants do well when they are first planted close to or underneath black walnut trees. The largest of the twenty Juglans species that are endemic to the United States is Juglans nigra, also referred to as black walnut. It can easily reach a height of 100 feet, and its spectacular canopy and strong, straight trunk brighten almost any landscape with an adequate scale.
Due to its regularity, sturdiness, and opulent chocolate-brown heartwood color, it is highly prized by the high-end furniture industry. Many landowners who have a few extra acres are investing in the growth of genetically better black walnut trees, which will reach maturity in 25 to 30 years.
When planted near or underneath the canopy of black walnut trees, horticulturists found that certain plants did not thrive while others faded and died. Juglone is a biological compound secreted by black walnut trees. These fluids can leak out of the roots underground as well as occasionally flow from the leaves down onto the plants and the ground below. Allelopathy is the term for the process.
Although many plant species are poisoned by juglone, this makes planting beneath black walnut trees challenging. There are still a lot of shrubs and perennials that can be planted without risk next to or under black walnut trees since they are juglone-resistant.
Apples, white birch, mountain laurels, blackberries, blueberries, tomato plants, azaleas, chrysanthemum, crocus, hydrangeas, lilacs, and rhododendron should not be planted next to or underneath the canopy of black walnut trees.
The majority of grasses, asters, shasta daisies, vinca, hostas, phlox, wisteria, morning glory, ajuga, solomon’s seal, and Virginia creeper are a few plants that can be grown next to black walnut trees.
Arborvitae, white ash, american beech, catalpa, black cherry, flowering dogwood, hibiscus, red maple, japanese maple, oaks, privet, eastern redbud, sumac, sycamore, tulip tree, rosa rugosa, viburnum (excluding maresii), and heucheras are among the plants and shrubs that tolerate it.
The survival of your trees and plants will be impacted by a number of factors in addition to the presence of Juglone, so proceed with caution. There are many factors that affect growth, including soil, moisture, temperature, shadow, and sunlight.
For a list of plant species that will grow beneath the shade of black walnut trees, go to Greenwood’s article on planting under these trees.
Does juglone affect hydrangeas?
In many American landscapes and parks, black walnut trees may be found. They make a great choice for a shade tree. Black walnut trees come with a curse called juglone, despite having some advantageous qualities including shade, fruit for wildlife, and the potential for wood harvesting income.
Black walnuts naturally release juglone as a poison to drive out rival plants. Asparagus, rhubarb, peppers, tomatoes, eggplant, potatoes, hydrangea, peonies, lilacs, blueberries, azaleas, and true lilies shouldn’t be planted near a black walnut tree.
We’ll go over the plants you can and cannot grow beneath black walnuts, regardless of whether you’re planning to plant one or already have one of these monstrosities growing. Let’s start now!
What perennial plants can be found close to black walnut trees?
Will flowering plants such as dogwood, butterfly bush, or lilac grow underneath a black walnut tree. The intended planting bed is only 12 feet away from the tree limbs.
As you are aware, juglone is present in black walnut roots, leaves, and bark. Many plants are poisoned by this chemical. Research on plants that can withstand the chemical juglone is scarce. The garden should be kept at least 50 feet away from the tree and ideally 80 feet away for the greatest results. The floral plants and shrubs on the following list have been seen to flourish beneath black walnut trees. Weeping forsythia, Koreanspice viburnum, various kinds of viburnum, redbud (choose the Columbus or Minnesota strain for improved hardiness), and Rose of Sharon. The following perennials can also flourish next to a black walnut. tulips, sundrops (Oenethera), trillium, lamb’s ear, Dutchman’s breeches, cranesbill geranium, hosta, daylilies, and sundrops (Astilbe). See the Black Walnut Toxicity bulletin from Purdue University for a more comprehensive list.
What bushes will flourish beneath a walnut tree?
Juglone-Tolerant Shrubs
- Barberry (Berberis spp)
- Hazelnut (Corylus americana)
- Daphne (Daphne spp) (Daphne spp)
- Forsythia (Forsythia spp)
- Witchhazel (Hamamellis spp)
- The Sharon Rose (Hibiscus syriacus)
- Winter Hydrangea (Hydrangea arborescens)
- John’s wort (Hypericum prolificum)
What kinds of plants can grow beneath a black walnut tree?
There are numerous strategies for avoiding toxicity. One method—possibly the simplest method—is to exclusively plant plants that are compatible with black walnut trees when gardening around one. Any known plant that grows beneath black walnut trees without toxicological damage is considered a black walnut tree friendly plant.
Sugar maple, blooming dogwood, and boxelder are just a few examples of flora that can tolerate black walnuts. You can also grow begonias, hyacinths, and crocuses. These are all recognized as black walnut-tolerant plants. There are a lot more, and your neighborhood garden center may let you know about any unpalatable plants so you don’t have any issues.
How is juglone neutralized?
Q. Due to the toxicity that the enormous black walnut trees emit, we have had difficulty getting anything to grow nearby. Is there any other option besides chopping them down to get rid of it?
A chain saw won’t help since the poison, known as juglone, is difficult to neutralize and can linger in the soil for years. Juglone is found throughout the entire tree, but it is most potent in the roots, which protrude well below the canopy.
Fortunately, juglone tends to remain in one place and is not a lethal substance to all. You now have two options for coping with this: choose juglone-tolerant plants for the area, and keep delicate plants outside the death zone.
Do hostas tolerate the shade of black walnut trees?
There are an astonishing number of varietal variations in hostas. Numerous variegated varieties are also available, with foliage colors ranging from light cream to blue. Hostas are fairly hardy plants that can thrive in both sunlight and shade, however new plantings in direct sunlight will require regular watering. Flowers come in a variety of sizes and beautiful hues, including white, pink, and lavender.
Because they are resilient, drought-tolerant, and appear to be immune to juglone, hostas are the most dependable perennials for growing beneath a black walnut tree. The hardiness zones for hostas are 4 through 9.
Are azaleas resistant to juglone?
Vegetables including tomatoes, potatoes, eggplants, and peppers as well as ornamentals like lilacs, peonies, rhododendrons, and azaleas are particularly sensitive to juglone. Juglone sensitivity in plants can cause a variety of symptoms, including stunting, yellowing, partial or complete wilting, and even mortality.
Juglone tolerance in roses?
Black walnut trees are a common addition to Midwest yards. Large and attractive in its native environment, the black walnut (Juglans nigra) tree produces edible nuts.
Black walnuts only have one drawback: they have strong territorial instincts. According to Doris Taylor, manager of the Plant Clinic at The Morton Arboretum in Lisle, many plants are unable to grow close to them. A substance called juglone, which the tree creates to protect its roots from competition, wards them off.
According to Taylor, juglone in the soil can cause many different annuals, perennials, shrubs, and vegetables to wilt, yellow, and eventually die.
That is not to say that a lovely garden cannot be built around a black walnut tree. Simply select plants that can withstand juglone.
Native plants of the Midwest, for instance, developed alongside black walnuts. Numerous other trees and plants are unaffected as well. “More options might exist than we realize, Taylor suggested. “Tolerance to juglone has not been investigated in many plants.
Japanese maple (Acer palmatum), pagoda dogwood (Cornus alternifolia), ninebark (Physocarpus opulifolius), and redbud are examples of large shrubs or small trees (Cercis canadensis).
Medium-sized to tiny shrubs include the Annabelle species of hydrangea and the beautybush (Kolkwitzia amabilis), shrubby St. John’s wort (Hypericum prolificum), spicebush (Lindera benzoin), and wild hydrangea (Hydrangea arborescens).
How far away from a black walnut tree should you plant?
- English walnut trees should be 20 to 40 feet apart, and black walnut trees should be 40 to 80 feet apart.
- REMEMBER: Grow black walnut trees 50′ away from fruit plants. Many plants are poisonous to black walnut tree roots.
- To fit the root system, create a hole that is both wide and deep.
- Before planting, thoroughly wet the roots.
- Numerous nut trees only have one primary root, which resembles a very long, skinny carrot. This taproot shouldn’t be cut or bent when planting most nut trees.
- To avoid matting, spread the roots out in the hole. Main taproot should not be bent or cut.
- Plant them at the same depth at which the nursery raised them. Plant bare root trees where the depth of the color difference between the roots and the trunk is most evident. A potted tree should be placed at the same depth as its pot of origin.
- Fill the hole with improved soil. With each shovel of dirt you add, thoroughly tamp the soil around the roots.
- Add two buckets of water when the hole is 3/4 filled. Treat the last bucket with Stark Tre-Pep Fertilizer and let it soak in. (For optimum results, wait until spring to fertilize if planting in the fall.)
- Complete the hole filling.
After Planting
- Cut off between one-third and half of the top of your new bare root tree when pruning it, but not any lower than the bud/graft union. This is necessary. This forces the sprout of your tree to grow strongly and develop into the main stem. Trust us when we say that rigorous pruning at the time of planting gives your new tree the greatest possible start. Nut trees in containers don’t require pruning.
- To protect it from sunburn and rat damage, paint the trunk with white latex paint or wrap it in Stark Tree Guards up to four inches from the top.
- About June 1, mulch. During the first few years, use mulch or regular cultivation to keep any weeds away from trees.