here on the edge of the boreal forest, moss and lichens grow everywhere except in blazing sun, and even then are likely to be present under grass and in cracks and crevices etc..--i deliberately took some bits of moss growing on old pavement (in the sun) and put them in a big pot with sempervivum etc..
i never would have thought of it as a problem--but marianne's climate in vermont is probably much wetter than mine, overall--my moss isnt choking anything out..
