Lythrum salicaria or purple-loosestrife is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the genus Lysimachia in the family Primulaceae. This herbaceous perennial plant is native to temperate regions of Europe, Asia, northern Africa, and eastern Australia.
Lythraceae is a family of flowering plants, including 32 genera, with about 620 species of herbs, shrubs, and trees. The larger genera include Cuphea (275 spp.), Lagerstroemia (56), Nesaea (50), Rotala (45), and Lythrum (35). It also includes the members of the former families of the pomegranate (Punica granatum, formerly in Punicaceae) and of the water caltrop (Trapa natans, formerly in Trapaceae). Lythraceae has a worldwide distribution, with most species in the tropics, but ranging into temperate climate regions as well.
The family is named after the type genus, Lythrum, the loosestrifes (e.g. Lythrum salicaria purple loosestrife) and also includes henna (Lawsonia inermis). It now includes the pomegranate, formerly classed in a separate family Punicaceae. The family also includes the widely cultivated crape myrtle trees. Botanically, the leaves are usually in pairs (opposite), and the flower petals emerge from the rim of the calyx tube. The petals often appear crumpled.