Black Walnut Tree Toxicity: Why Won't Plants Grow Near My Black Walnut Tree?


Date: February 12th, 2010 Black Walnut TreeBlack walnut trees produce and store a toxin called juglone (5-hydroxy-alphanapthaquinone) in their roots. Juglone has no effect on the health of the black walnut tree but is a very harmful chemical to many other plants. For this reason, it is very difficult to grow healthy plants within close vicinity of a black walnut tree. In fact, although most sources agree that the soil is clean beyond the tree’s drip line, some gardeners have found that a radius as large as eighty feet from the trunk may be affected. Additionally, as the tree grows from year to year, the affected area also enlarges as the root system extends outward below the surface.



Plants suffering from juglone toxicity may show a variety of symptoms. The extent of damage depends on the resistance of individual plants and the amount of contact with the toxin. Although juglone is not water-soluble and therefore will not readily travel through soil, it is believed that even a minor amount of contact with decaying leaf litter, nut husks, or rain drops containing juglone can harm extremely sensitive plants. Look for wilting, droopy, puckering, or twisting leaves that appear yellow or discolored. Internal stem tissues on woody plants or shrubs may also show darkening or discoloration.



However, some plants are immune to juglone. To find out which plants are susceptible and which are immune, look below:



Plants to Grow under your Tree

(immune to juglone)

Plants to Avoid

(susceptible to juglone)


  • Cherries
  • Black raspberries


  • Lima beans
  • Beets
  • Carrots
  • Corn
  • Onions
  • Squash

Landscape Plants

  • Red cedar
  • Elms
  • Forsythia
  • Hemlock
  • Wild rose
  • Sycamore

Flowers and Herbaceous Plants

  • Wax begonia
  • Bellflower
  • Bluebells
  • Kentucky bluegrass
  • Shasta daisy
  • Daylily
  • Ferns
  • Hollyhock
  • Iris
  • Pansies
  • Morning glory
  • Violets
  • Zinnia



  • Apple
  • Blackberry
  • Blueberry
  • Grapes


  • Eggplant
  • Cabbage
  • Green peppers
  • Potatoes
  • Tomatoes
  • Cucumber

Landscape Plants

  • White birch
  • Silver maple
  • Basswood
  • Red pine
  • Scotch pine
  • White pine
  • Norway spruce

Flowers and Herbaceous Plants

  • Azalea
  • Rhododendron
  • Crocus
  • Peony
  • Lilac
  • Alfalfa



If you have any further questions regarding your black walnut tree, email me at, or visit your local CountryMax store today!



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