Lythrum

Scientific name

Lythrum L.

Common names

loosestrife

Family

Lythraceae

Could be confused with

Ammannia, Didiplis, Ludwigia, Nesaea, Rotala

Native distribution

North America, Europe, Africa, Asia, Australia

Species commonly cultivated

Lythrum alatum Pursh. (North and South America)

L. salicaria L. (Eurasia, North America)

L. virgatum L. (Asia, Europe)

Adventive distribution

Lythrum salicaria is introduced into North America.

Weed status

Purple loosestrife (Lythrum salicaria) is a declared noxious weed in many countries, including many states in the United States.

Habit

small herb to medium sized shrub, emergent

Brief description

Stem erect, creeping or floating. Leaves opposite, whorled or alternate, usually sessile; leaf blade linear to ovate or obovate; base acute, obtuse to cordate. Flowers actinomorphic or slightly zygomorphic, solitary in leaf axils or in complex inflorescences, usually a terminal spike. Sepal tube campanulate to tubular, lobes 6 (4); petals usually 6 (4), pink to purple. Propagules are seeds.

Natural habitat

littoral, wet ground, and marginal shallows

Additional comments

Lythrum contains 38 species, with about six aquatic. Lythrum virgatum is similar to L. salicaria but has narrower, glabrous leaves with acute base and flowers in a leafy raceme.