Walnut trees naturally produce a chemical called Juglone, which inhibits or prevents the growth of other plants. Juglone is found in Walnut leaves, fruits and other parts. Many plants are intolerant of Juglone, making landscaping under Walnuts a real challenge. If allowed, Juglone can build up in the soil to levels toxic to other plants. When planting underneath Walnut trees, regularly pick up any fallen leaves, fruit or branches and dispose of them. Do not add Walnut debris to your compost pile.
The following lists will help you to chose the right plants for your particular situation:
Beets, Black Raspberry, Corn, Onions, Lima Beans, Parsnips, Snap Beans, Wheat, Wild Yam
Arborvitae, Aster, Barberry, Brown-eyed Susan, Campanula, Christmas Fern, Cinnamon Fern, Clematis, Common Mallow, Coral Bell, Crabapple, Crocus (some), Currant, Daylily, Dianthus, Dogwood, Elderberry, Evening Primrose, Forsythia, Geranium, Geum, Grape, Grape Hyacinth, Hazelnut, Heal All, Honeysuckle, Hydrangea, Iris, Jack-in-the-Pulpit, Joe Pye Weed, Kentucky Bluegrass, Kerria, Liriope, Lobelia, Mayapple, Pachysandra, Peppermint, Phlox, Potentilla, Ranunculus, Rose, Sedge, Sedum, Sensitive Fern, Shasta Daisy, Shield Fern, Spicebush, St John’s Wort, Sumac, Sunflower, Tall Oatgrass, Trillium, Verbascum, Viburnum (some), Violet, Virginia Creeper, Wild Ginger, Wood Sorrel, Yarrow
Apple, Asparagus, Blackberry, Blueberry, Cabbage, Eggplant, Grape, Pear, Pepper, Potato, Rhubarb, Thyme, Tomato
Azalea, Birch, Buttercup, Chrysanthemum, Columbine, Crocus (some), Hydrangea, Kalmia, Lilies, Lily-Of-The-Valley, Linden, Narcissus, Nicotiana, Peony (some), Petunia, Pine, Potentilla, Rhododendron