I find 8-foot canes make a perfectly adequate wigwam. I grow two plants per cane, and its usually sensible to put in some extra seeds as germination isn't always that good. If you put start them in pots under cover about the end of April or the beginning of May, they're usually ready to plant out at the right time. Unless you get a summer like the last one, that is, when my beans were hit badly by June frosts.