Where to put gardening questions? Watch
Hobbies and interests would be a good place, but you can put something in just H&I without it going in a sub-forum, but none of them are relevant. I've created a gardening society, and I did manage to put that in just the H&I section. Luckily you can link threads from other sections to the groups.
So AOEI if it's more important, and then Chat, for more random, unimportant gardening stuff?