How big does swamp milkweed,butterfly weed get?
I have a small area of my yard that I'm attempting to convert to a butterfly garden this year. So far, there is a butterfly bush in the center surrounded by black-eyed susans and purple coneflowers. I haven't had much luck yet with the butterflies. I was thinking of adding either a butterfly weed (Asclepias tuberosa) or a swamp milkweed (Asclepias incarnata) or hopefully both. I'm almost out of room though. I've read they get from 2-4 feet high, but I can't tell how wide they get. Some of the pictures I've seen look like they grow almost straight up. How much space do I need to give them?