Walnut Toxicity

Walnut Toxicity

To protect themselves from competition, black walnut trees exude a toxin called juglone.  Gardens planted near black walnut trees or roostocks frequently fail to thrive due to this toxin.  Many plants can be affected, but tomatoes and potatoes show the greatest susceptibility.

Juglone enters the soil from the roots, bark, leaves, and nut hulls of the walnut tree.  It cannot move far, as it is not water-soluble, but it impacts nearby garden plants by interfering with their respiration.  This weakens the plants and eventually causes their death.


  • Stunted growth.
  • Sudden wilting.
  • Twisted, yellow leaves.
  • Death.


Walnut Toxicity

There is no cure for walnut toxicity.  If it becomes a problem, the garden must be relocated or moved into raised beds.


If you can, choose a garden location away from walnut trees.  On small properties, this may not be an option, but you still have two other possibilities to consider:

  • Choose only plants tolerant of juglone (see Helpful Resources below).
  • Grow all plants in raised beds, regularly swept clean of leaves and nuts.

Even if your garden is in an ideal location, never use black walnut leaves, bark, or chips as mulch.

Helpful Resource

Black Walnut Toxicity
Handy factsheet offering more information, including lists of plants susceptible and resistant to juglone.

Complete Series

Garden & Orchard Diseases

Garden & Orchard Diseases

By hsotr

Pulling from nearly 20 years of experience, Michelle Lindsey started Homestead on the Range to help Kansans and others around flyover country achieve an abundant country lifestyle. Michelle is the author of four country living books. She is also a serious student of history, specializing in Kansas, agriculture, and the American West. When not gardening or pursuing hobbies ranging from music to cooking to birdwatching, she can usually be found researching or writing about her many interests.