More like an ad-hoc endocrine system then any kind of speech. Honestly don't really like how that mechanism is portrayed as speech. Certainly it helped the person who figured it out sell a lot of books, but it's quite the misnomer.
Imagine the first time a tree gets to talk to the other trees. Like, it talks to itself for a decade or two before someone touches it and now it can hear dozens of voices.
honestly it's less magic and more cosmic horror, fungi are literally the source of most of the organic decay we're used to (especially rotting trees), and the fact that they effectively are the ground in many places is not in any way magical because aaaaaaa