Walnut Toxin Juglone

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Posted in Walnuts | Posted on 10-09-2009

After the failure of our first garden, which was planted near several very tall Black Walnut trees, we finally found that the cause of our plant die-off was due to the walnut toxin juglone.

Juglone is present in all parts of Black Walnut and Butternut trees, including the roots, bark, leaves, branches & nuts.  Juglone can be found up to 80 feet away from a walnut tree’s trunk, so if you plan to garden near walnuts, be sure to keep your distance from walnut trees, or try planting only juglone tolerant species.

Another work-around, is to plant in pots or other containers.  Raised beds will also work, if you use non-juglone-contaminated soil, if the bottom of the raised bed is sealed off from the ground so there is no way for your plants’ roots to touch a walnut tree’s roots, and if you pick out any fallen leaves or nuts from your containers.

Compost made from the leaves of Black Walnuts can be used if they are allowed to break down for a minimum of 1 month, but if there are any nuts or nut hulls, twigs or bark in the compost, it’s best to let them breakdown for about 6 months before using that compost near any plants that may be juglone sensitive.

Here is a partial list of plants that DO NOT grow within a 50 to 60 foot radius around Black Walnut trees:

  • Asparagus
  • Beans*
  • Blackberry
  • Blueberry
  • Broccoli
  • Cabbage
  • Cucumber*
  • Eggplant
  • Grapes
  • Peppers
  • Potato
  • Rhubarb
  • Rutabaga
  • Tomatoes
  • Turnip
  • Apple trees

*Some varieties of beans and cucumbers have been said to be juglone sensitive, although the evidence is inconclusive.  Our cucumbers were affected, but our beans survived just fine.

More information can be found here.

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