How Close Do Companions Need to Be?
I've been reading about companion planting. It makes sense and I plan to try it.
I'm more concerned about the bad companions. They say beans and onions don't like each other, but beans and carrots do (as well as carrots and onions). I plan on planting a row pole beans (along a fence line for support), with a row of carrots beneath them. If I planted onions on the other side of the carrots (so the carrots are between the beans and onions) would that put the beans and onions far enough apart? The beans and onions would be a foot or two apart with carrots in between.
B B B B B B B B B B B B B B Beans
C C C C C C C C C C C C C C Carrots
O O O O O O O O O O O O O O Onions
Also, how close do good companion plants (like tomato and basil) need to be to gain benefits from each other? Does the magic happen underground (root level, stuff exuded into soil) or it is only related to the fragrance of the plants?