I grow common burdock by accident because it is a common weed. Is that the same one that burdock root comes from? (after I asked the question, I looked it up, so what follows is me thinking out loud) It is interesting -- if you type burdock root into Google, you get a bunch of listings about medicinal uses of it. If you type burdock weed into Google you get listings about it as a noxious weed and how to control it.
I guess they are different burdock species-- the common weed is arctium minus (lesser burdock) and the burdock root plant is arctium lappa(great burdock).
But it's hard for me to believe that the species are that different that it might not become a big pest in your garden. You know burdock is where the idea for Velcro came from. Its burrs (from whence it is called bur-dock) have hooked spines that cling into everything, cloth, animals' fur, etc and are difficult to remove. Some creative science type decided to imitate how that works and came up with Velcro. The usefulness of Velcro does not cancel out the pestiness of burdock spines!
But I didn't know my burdock weed was edible/ medicinal. Apparently it has similar uses to arctium lappa. I've always left a little bit of it around because it is a butterfly plant.
I will have to look at mine more closely next year - I've heard people around here refer to our weed as great burdock. I'm not sure if that's just a mistake or if we might have both species around here...