What species of mycorrhizal fungus do well with apple trees?
How do I innoculate a 3 year old tree with a mycorrhizal fungus?
These two questions were closed as off topic and pointed to Gardening.SE. However, these are permaculture questions. The question of encouraging fungal symbiosis is one that permaculturists deal with regularly, but conventional gardeners often aren't even aware of.
Almost every question on permaculture could easily and readily fit with in the scope of gardening. However, currently, there are 4 questions with in the permaculture tag. Askers of permaculture questions are likely to get a lot of very unpermaculture answers over there. I think permaculturists are much more likely to be attracted to a site focused only on sustainable answers to problems than they are to a generic gardening site. And thus, we should allow permaculture questions over here, where they will get more of the focus the asker is looking for.
That does mean allowing a lot of questions that on first glance would fit perfectly in Gardening.