I knew I would have to come to my true confessions, I am an English major lawyer. A recovering lawyer, though....
They are a plant that is not native. I don't think it's native at all to the U.S. or Canada. It has been introduced. Maybe John can bail me out on this but it is a tall and unfortunately very beautiful plant that has these leafy ends. It is not like the purple loosestrife, which is pretty too, unfortunately. It is better if they are not pretty. The phragmites are very tall and they have thousands of seeds on them. The establish themselves and basically squeeze out all the other plants. I don't know technically if there's a biologist in the house who can bail me out.
John, are you familiar with this?