This is an unusual and lovely wildflower that grows in wet areas... It's also known as the "Great Lobelia" and it is pretty great to look at. It is a North American plant and was originally thought to be a treatment for VD, hence the name "Lobelia siphilitica." Perhaps they were trying to create a market for the plant. Anyhow, when they tested the plant in europe it was found to be ineffective.
