A walnut tree, whether black or common, can be a stately and outstanding focal point in a yard. Landscaping around walnut trees, however, brings the gardener into the world of self-protective plant chemistry. Producing juglone, a phytotoxin, in roots, branches, and leaves, walnut trees literally defend their turf and solitary status from potentially competing plants. Choose carefully among shrubs known to tolerate this growth-stunting chemical to make your walnut tree part of an overall landscape plan.
For screening or property definition, shrubs known mostly for their foilage are often used for hedging. Consider Juniperus virginiana varieties, American arborvitae, and Euonymus hamiltoniana (Euonymus europaea, once recommended, has become invasive in some regions). American holly is also known for juglone tolerance, as is Canadian hemlock, available in dwarf varieties.
Flowering shrubs that do well when planted close to walnut trees include several old-fashioned favorites: forsythia, daphne, rose of Sharon, and mock orange. Slightly less well-known are koreanspice viburnum and both single and double forms of kerria. Numerous varieties of lilac also demonstrate juglone tolerance.
Other Interesting Juglone-Tolerant Shrubs
While it is hard to generalize about whole families of shrubs, it is important to remember that many families have one or more members that tolerate proximity to walnut trees. A garden containing a walnut tree, therefore, does not need to be spare or monotonous. Native plants like spicebush, sand cherry, and American elderberry attract birds with berries. Climbing vines, such as clematis and honeysuckle, appear to tolerate juglone well; check, however, the invasive status of these climbers in your area.