Alleopathic?
I found one reference to this, just the one.
I was going to top dress some grow barrels with sycamore leaves, but I would hate to set back my plants with an avoidable mistake.
The Ferns website makes no mention of allelopathy with sycamore. I did find this pdf:walterreeves.com which suggests a moderate effect from roots and leaves of sycamore, but it also lists oak, hazel and chestnut so I wouldn't be too concerned myself.
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