Care to share a spoiler? :-)
I think the consultant in question had a bit of a thing about people consuming large quantities of "natural" products and being surprised that this could make them quite ill and indulged in a bit of a rant.
There actually is a tree which will kill you if you hang around it for long enough (the manchineel tree), but to be fair I wouldn't expect to find it in somebody's garden.
https://www.atlasobscura.com/articles/whatever-you-do-do-not...