LOOSESTRIFE.

I've always loved the word "loosestrife," without having a mental picture of the actual plant (sadly often the case with me and plant names). Now I have two. I'm visiting my wife's family in the Berkshires (the wooded hilly region of western Massachusetts), and I was told that the attractive purple flowers fringing the pond were purple loosestrife, an invasive species that "now poses a serious threat to native emergent vegetation in shallowwater marshes" throughout the northeast. And when I asked what the pretty clusters of small white flowers in a vase were, I was told they were gooseneck loosestrife. Gooseneck loosestrife! Isn't that a wonderful phrase? I've been mumbling it to myself ever since. (And they do look astonishingly like the heads of geese.)

Addendum. Incidentally, "loosestrife" is an interesting word; it pretends to be a translation of lysimachia, but that Greek word is actually derived from a personal name, Lysimachus (or Lysimakhos if you're into that sort of thing).