To what degree is Blue elderberry Allelopathic?
Hello! I have two large (about 20 ft high) elderberry trees growing in my urban 5000 sq ft lot in north portland. I had noticed that not a lot of things grow underneath them and always wondered why, and recently learned about Allelopathic plants, and blue elderberry being one. I am considering taking them out if they truly are effecting the growth capabilities of other plants and soil health. I have read that their leaves are the most toxic part, which fall across the yard along with lots of small branches, and make a mess late summer- fall. I also had some trimmed and spread wood chips from it in my yard last year. If I were to take them out now, how long would the toxicity levels continue to effect other plants in the area? Any advice on this?
Multnomah County Oregon
Thank you for your question. I have been unable to find any reputable source indicating this plant is alleleopathic. This USDA article mentions nothing about it. Could you send a source that indicates it is? Another more probable reason for the problems you have are a lack of water and light. I cannot advise about mulch without knowing what sources you know about plant impact on plants. Thanks!
So, here is my technical/ethical problem. As a Master Gardener, I am required to give advice based on scientific research or governmental agencies’ information. There are many societies, webpages and commercial groups which represent/advocate for/promote various viewpoints which may or may not be grounded in science. You can believe and/or act on loads of advice out there, but the most reliable information I am able to provide is the link I don’t think was attached: https://cybercemetery.unt.edu/archive/allcollections/20090115204112/http://plants.usda.gov/plantguide/pdf/cs_sanic5.pdf Take a look and tell me what you think.
Thank you. That makes sense that the USDA article would be more solid. Normally, do their articles say that plants are allelopathic?
Yes, they would indicate that. The juglans (walnut) family is the best known with this characteristic, and you can see what they indicate about juglone here: https://plants.usda.gov/plantguide/pdf/cs_juni.pdf Hope this is helpful!
In reading the Herb Society article again, I think the confusion may result from interchanging ‘toxicity’ with ‘allelopathy.’ We can eat walnuts, which also contain juglone, but it is not toxic to us. The nightshade family (tomatoes, peppers, potatoes) contain a chemical (belladonna) which, in sufficient quantities, can be toxic. Belladonna is toxic, but the plant has no detrimental effect on surrounding plants. BTW, here is the current article on elderberries; I inadvertently sent an archived version: https://plants.usda.gov/plantguide/pdf/cs_sanic5.pdf