Black walnut trees (Juglans nigra) are popular landscape trees that emit juglone, a toxic substance that helps reduce the tree’s competition for nutrients. The juglone is emitted from the tree's roots, nut hulls and buds. The toxin collects in the soil underneath the tree's canopy and can spread up to 60 feet away from the tree’s trunk. Many plants are sensitive to juglone and turn yellow, drop their leaves and gradually die. However, some plants tolerate black walnut toxicity.
The word daylily (Hemerocallis) is derived from two Greek words that mean “beauty” and “day,” which refers to the fact that each daylily bloom lasts for one day only. These perennials come in a wide range of colors, sizes and shapes. Daylilies can survive in a wide range of climates with very little care. Because these plants are so hardy, daylilies are ideal for planting near black walnut trees.
A daffodil (Narcissus pseudonarcissus) is another hardy perennial that tolerates black walnut toxicity. These plants are easy to grow, making them ideal for beginner gardeners in most areas of the United States (US). While daffodils can survive in the shade of trees, they grow better outside of the drip line rather than underneath them.
Jack-in-the-pulpits (Arisaema triphyllum) are perennial herbs that are easily cultivated and take very little care. This plant survives under various conditions, and thrives in shady, moist areas, including underneath black walnut trees. Jack-in-the pulpits have hooded, cylindrical blossoms that are green with brown stripes. They also grow a cluster of red berries late in the summer.
Honeysuckle vines are perennials that bear sweetly scented, trumpet-shaped flowers and a decorative fruit that attracts birds. Flower colors are usually shades of white, yellow, red or pink. The honeysuckle vine works great as a ground cover, and the hardiness of this plant makes it able to tolerate the black walnut toxicity. These plants are especially hardy in zones 5 through 8.
Virginia creepers (Parthenocissus quinquefolia) are perennial vines in the grape family. These vines typically climb shrubs, trees and fences, but occasionally form a ground cover up to 1 foot tall. Virginia creepers bloom flowers with small, triangular-shaped petals. These vines prefer partly sunny areas with loam or clay-loam soils. However, the Virginia creeper adapts well to various growing conditions and is hardy enough to grow near black walnuts.
Wild grape (Vitis rotundifolia), also called southern fox grape and muscadine, is a high-climbing vine that can grow up to 100 feet long. Leaves are dark green and smooth with slightly hairy undersides. It typically bears black-purple grapes that ripen from July through late September. This hardy plant can grow underneath black walnut trees.
Shasta daisies (Chrysanthemum maximum) are popular perennials native to Europe and naturalized throughout the United States (US). These daisies have gold centers surrounded by white petals. These hardy plants are able to tolerate the black walnut toxicity and do especially well in zones 5 through 9. Shasta daisies prefer well-drained, most soil with very light shade. The flowers bloom in June and July, but the foliage remains green all year.