loosestrife, common name for the Lythraceae, a widely distributed family of plants most abundant as woody shrubs in the American tropics but including also herbaceous species (chiefly of temperate zones) and some trees. Several shrubs of this family have been introduced in the United States as ornamentals and are now naturalized, e.g., the crape (or crepe) myrtle of China ( Lagerstroemia indica ) and the henna shrub, or mignonette tree ( Lawsonia inermis ). The latter, cultivated especially in Muslim countries, is the source of henna dye (from the leaves), oil and pomade scents (from the flowers), and a medicament (from the bark). The wild marsh plants called loosestrifes (genus Lythrum ) include several native American species with pink or lavender flowers, but the tall, showy species that blankets moist meadows and swamps with magenta to purple flowers in late summer and autumn is the spiked loosestrife ( L. salicaria ), introduced from Europe and now so widespread as to be a weed. Several species of the unrelated family Primulaceae (primrose family) are also called loosestrife. True loosestrife is classified in the division Magnoliophyta, class Magnoliopsida, order Myrtales.