The loosestrife epithet is applied to two very different groups of plants. Prairie loosestrife and its Lysimachia kin would seem to have first claim. After all, loosestrife is apparently a screwed-up translation of Lysimachia. Somehow, loosestrife has also become the name of plants in the genus Lythrum. The family of Lythrum, Lythraceae, has even taken on the loosestrife name. One of the well known Lythrums is that nasty invader of wetlands, purple loosestrife, which you see here. This all leads many to think there's a realationship between the purples and yellows that's not there.