Loosestrife, the common name of a group of plants related to the common primrose; also, the name of an unrelated plant family. The primrose loosestrifes include the North American four-leaved loosestrife and the moneywort, naturalized in North America from Europe. Plants of the loosestrife family include the purple loosestrife, a Eurasian plant naturalized in North America, and the North American milk willow herb.
Primrose loosestrifes belong to the genus Lysim-achia of the primrose family, Primulaceae. The four-leaved loosestrife is L. quadrifolia; moneywort, L. nummularia. The loosestrife family is Lythraceae. The purple loosestrife is Lythrum salicaria; milk willow herb, L. alatum.Garden loosestrife is a member of the primrose family with leafy stems and yellow or white flowers.