You're right about the homesteading / gardening folks being a tight community. That's a recent development though - just this past summer.

I'd suggest they check out some of the contests and challenges. There's usually lots of interaction from folks with all different types of interests - especially the meme contests and the photography challenges. It's a good way to have something to post about every day. They're bound to strike up some friendships and that leads to the like-minded communities. Persistence and patience do pay off!