I'm missing the hint for allelopathie, the research of reciprocal influences
of plants, practicized by friends of "Mischkultur", mainly explained by
mycorrhizal effects in the edaphone - founded by H. Molisch, university of
Vienna,

Sounds like a bunch of hooey.

you can hear more of this from orchid friends, it's their primary focus

You are confused. Orchids are generally grown in individual pots, grouped
together in a greenhouse or growing area simply for covenience & control of
lighting & humidity. Most amateurs have a collection of various different
orchids. Now when you talk about orchid growers, they have a very strong
tendency to congregate in groups, local groups once a month, national or
regional groups once a year. Individual growers languish & show signs of severe
depression if they are forced to exist alone. This phenomenon is found among
many kinds of growers, not just of orchids.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)