Companion plants for black walnut trees
Purdue University has informal lists of plants that tolerate juglone and those that are sensitive to it. Choose from the following list for best results in planting near black walnut trees or walnut trees grown on black walnut rootstock. Follow these guidelines for planting within the dripline of the tree and, according to the University of Wisconsin, up to 50’-80’ from the trunk. Naturally you need to consider the sun and shade requirements of the plants, as well.
Vegetables: lima bean; snap bean; beet; carrot; corn; melon; onion; parsnip; squash.
Fruits: black raspberry, cherry.
Landscape plants: arborvitae; autumn olive; red cedar; catalpa; clematis; crabapple; daphne; elm; euonymous (burning bush); forsythia; hawthorn; hemlock; hickory; honeysuckle; junipers; black locust; Japanese maple; maple (most); oak; pachysandra; pawpaw; persimmon; redbud; rose of sharon; wild rose; sycamore; viburnum (most); Virginia creeper.
Flowers and herbaceous plants: astilbe; bee balm; begonia; bellflower; bergamot; bloodroot; Kentucky bluegrass; Spanish bluebell; Virginia bluebell; bugleweed; chrysanthemum (some); coral bells; cranesbill geranium; crocus; Shasta daisy; daylily; Dutchman’s breeches; ferns; wild ginger; glory-of-the-snow; muscari (grape hyacinth); grasses (most); orange hawkweed; herb Robert; hollyhock; hosta (many); hyacinth; Siberian iris; Jack-in-the* pulpit; Jacob’s ladder; Jerusalem artichoke; lamb’s ear; leopard’s bane; lungwort; mayapple; merrybells; morning glory; narcissus (some); pansy; peony (some); phlox; poison ivy; pot marigold; polyanthus primrose; snowdrop; Solomon’s seal; spiderwort; spring beauty; Siberian squill; stonecrop; sundrop; sweet Cicely; sweet woodruff; trillium; tulip; violet; Virginia waterleaf; winter aconite; zinnia.
Plants that are sensitive to black walnut tree toxicity
Vegetables: asparagus, cabbage, eggplant, pepper, potato, rhubarb, tomato.
Fruits: apple, blackberry, blueberry, pear.
Landscape plants: black alder; azalea; basswood; white birch; ornamental cherries; red chokeberry; hackberry; Amur honeysuckle; hydrangea; Japanese larch; lespedeza; lilac; saucer magnolia; silver maple; mountain laurel; pear; loblolly pine; mugo pine; red pine; scotch pine; white pine; potentilla; privet; rhododendron; Norway spruce; viburnum (few); yew.
Flowers and herbaceous plants: autumn crocus (Colchicum); blue wild indigo (Baptisia); chrysanthemum (some); columbine; hydrangea; lily; narcissus (some); peony (some); petunia; tobacco.
Field crops: alfalfa; crimson clover; tobacco.
Tip: This does not mean you can’t compost black walnut leaves. According to Ohio State University Extension, “walnut leaves can be composted because the toxin breaks down when exposed to air, water and bacteria. The toxic effect can be degraded in two to four weeks.” If you do compost the leaves, put them in a separate compost pile and do not spread the resulting compost on plants that are on the sensitive list.
For more information: The go-to book for anyone growing nut and fruit trees in California is the UC Davis publication, The Home Orchard.
Add some walnut trees to your property and create a beautiful landscape with these companion plants that tolerate toxicity.
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