The black walnut, though valued as a shade tree and as a source of hardwood and edible nuts, can be toxic to nearby plants. It produces juglone, a chemical which inhibits the growth of some, but not all plants growing in its vicinity.
Some plants are very sensitive to juglone and soon die when planted beneath a black walnut. Many others, however, have been observed to be unaffected by the chemical. It is always best to test a plant's resistance before planting a large number of them. Providing excellent soil drainage is one way to mitigate problems.
Some annual flowers that appear to be tolerant of juglone are wax begonia, morning glory, pansy and zinnia.
Perennials and Bulbs
Try the following if you must plant near a black walnut: daylily, ferns, iris, phlox, astilbe, monarda, dicentra, rudbeckia, hosta, daffodil and tulip.
Shrubs and Ground Covers
Some shrubs and ground covers that are tolerant include forsythia, most viburnums, pachysandra, euonymus, sweet woodruff and wild ginger.
Vegetables and Fruits
Those that have been observed to be tolerant of juglone include lima and snap beans, corn, onions, melons, and black raspberries.
Many native wildflowers seem to be unaffected, including Jack-in-the-pulpit, bloodroot, trillium, and mayapple.
- West Virginia University Extension
- Ohio State University Extension
- National Public Radio
black walnut toxicity, juglone, plants tolerant of black walnut
About this Author
Gwen Bruno has 28 years of experience as a teacher and librarian, and is now a full-time freelance writer. She holds a bachelor's degree from Augustana College and master's degrees from North Park University and the University of Wisconsin. She writes articles about gardening for DavesGarden.com.