Lythrum salicaria is a herbaceous, clump-forming, wetland perennial  plant, belonging to the Lythraceae (loosestrife) family. Plant is native to Europe, Asia, Northern Africa and Australia. Naturally found in ditches, wet meadows and marshes and along sides of lakes. It is also naturalized in many parts of the world, including Southern Africa, North and South America. It has been introduced in many areas of North America by beekeepers. The generic name Lythrum is derived from the Greek word ‘lythron’ meant blood in a sinister sense, i.e. impure, as from flowing battle wounds and other causes. As none of this group of plants has blood-red flowers, it is possible the name indicated that the plant was used for stopping blood. The specific epithet salicaria derives from the similarity of the leaves to willows.

Purple Lythrum can grow 1–2 m tall, forming clonal colonies 1.5 m  or more in width, with numerous erect stems growing from a single woody root mass. The stems are reddish-purple and square in cross-section. Lanceolate shaped leaves are hairy and stalkless, 3–10 centimetres long and 5–15 millimetres broad, they arranged opposite or in whorls of three. The flowers are reddish purple, 10–20 millimetres in diameter, with six petals and 12 stamens, they are clustered tightly in the axils of bracts or leaves. Flowering continues from May to September. The flowers are pollinated by long-tongued insects, including bees and butterflies. The fruit is a small 3–4 millimetres capsule containing thousands of minute seeds. A single plant may produce up to 2.7 million tiny seeds annually. Seeds are easily carried by wind and water; they germinate in moist soils after overwintering.

Lythrum salicaria is an easy garden plant, thriving in any soil. Prefers full sun, wet condition but withstand some dryness. It is a very cold tolerant plant, withstands up to -40 ºC. It grows naturally in bog gardens, on banks of streams and around ponds. When the seeds are mature, the leaves often turn bright red through dehydration in early autumn; the red colour may last for almost two weeks. The dead stalks from previous growing seasons are brown. Propagation is done by root division, cutting or seed. Cuttings may be taken from non-flowering laterals in midsummer.

Purple Lythrum is an invasive plant, that it can rapidly colonize in wet areas and both choke out native vegetation and destroy wildlife habitat. The plant is classified as noxious weeds in some States as like of Missouri and may not be sold in commerce.

Although Lythrum salicaria popularity as a medicinal plant has recently declined it has been used for centuries in European traditional medicine. It has been used as an astringent medicinal herb to treat diarrhea and dysentery. The extracts and some isolated compounds were shown to possess antidiarrheal, antimicrobial, antioxidant, anti-inflammatory and anti-diabetic activities.