This plant has nothing to do with Jerusalem and is not even an artichoke. It is in fact a type of North American sunflower and reputedly gets its name from the Italian word for sunflower - girasole. When first introduced to Europe the taste was likened to an artichoke and the name stuck. This explains why it is so different to a globe artichoke, which is a variety of thistle.
The important reason that we grow Jerusalem artichokes is that pigs love them. They produce a lot of biomass in a small amount of space with minimal effort. In fact while we try to harvest all of the tubers we don't plant any- they are one of those plants that are hard to get rid of. Next year they will just come up profusely in the same place. They are confined so far to one raised bed which may prevent their spread into other areas where they are less welcome.