Juglone - Ask Extension
I would like some information on the effect of juglone fromfruits and black walnut trees and their effect on plants located adjacent to the trees.
...
Knowledgebase
Juglone #852484
Asked October 07, 2023, 3:19 PM EDT
I would like some information on the effect of juglone fromfruits and black walnut trees and their effect on plants located adjacent to the trees.
I have looked on line and found some conflicting information. There appears to be some concensuous that Juglone originating from black walnut trees (Leaves, friuts and roots). adversly affect adjacently located trees and bushes, In particular, apples are mentioend to be particulary sensitive, but there are others as well.
I have also seen refernces that this a legend, based on hearsay and never confirmed by a serious, well researched study.
Can you please comment on this and direct me to some research on this topic?
Cayuga County New York
Expert Response
Hello Phil,
Thank you for your inquiry. This is not legend, juglone sensitivity of some plants is real. However, there are many plants that are tolerant of juglone. Unfortunately, most of our food crops are not tolerant to juglone but neither would they be tolerant of the shade produced by a mature walnut tree. An excellent article from Penn State Extension with a list of tolerant plants can be found here:
More information here:
https://hortnews.extension.iastate.edu/faq/what-plants-are-sensitive-juglone-produced-black-walnuts
Let me know if you have further questions.
Linda Svoboda
Horticulture Program Educator
Cornell Cooperative Extension of Broome County
Thank you for your very quick response. So nice living near a resource like Cornell!
The reason I asked was that I took a course from a professor in Washington who claims that there has never been any definitive work correlating Juglone with fruit tree toxicity (or any other plants for that matter). She claims it was based on conjecture and merely just repeated over and over. She says that she is in the process of having a peer reviewed paper published on this subject.
Here is a link to her work.
Please understand I am not calling into question your response, I just want to remove any doubt. In my own experience , my neighbor has several black walnut trees close by. I have had a HoneyCrisp apple tree die and an Empire apple tree die. But I also have another HoneyCrisp apple tree which is thriving. So two out of three say she is wrong! Or maybe I just took more care in planting the surviving tree!
I looked at the reference that you kindly sent me. Do you have any links to some basic studies?
Sorry to be a pest!
Kind regards,
Phil
