About Lythrum salicaria L.
Lythrum salicaria L. grows 1–2 m (3 ft 3 in – 6 ft 7 in) tall, forming extensive clonal colonies where numerous erect stems grow from a single woody root mass. Stems are reddish-purple and square in cross-section. Leaves are lanceolate, 3–10 centimetres (1–4 in) long, 5–15 millimetres (3⁄16–9⁄16 in) broad, downy, and sessile, arranged opposite each other or in whorls of three. The flowers are reddish purple, 10–20 millimetres (1⁄2–3⁄4 in) in diameter, with six petals (occasionally five) and 12 stamens, clustered tightly in verticillasters in the axils of bracts or leaves. There are three distinct flower types, each with stamens and style of different lengths: short, medium, or long. Each flower type can only be pollinated by one of the other two types, never the same type, which ensures cross-pollination between different plants. For example, if the pistil is medium length, the stamens will be long and short, not medium. Many types of insects visit the flowers, giving this species a generalised pollination syndrome. The fruit is a small 3–4 millimetre (1⁄8–5⁄32 in) capsule that holds numerous minute seeds. Flowering occurs throughout the summer. When seeds reach maturity in early autumn, leaves often turn bright red through dehydration, and this red autumn colour can last for almost two weeks. Dead stalks left over from previous growing seasons are brown. L. salicaria varies widely in leaf shape and the degree of hairiness, and a number of subspecies and varieties have been described in the past, but it is now generally considered monotypic, with none of these variants recognised as botanically significant. The species Lythrum intermedium Ledeb. ex Colla was often treated as synonymous with L. salicaria in the past, but the Plants of the World Online database now recognises it as a separate species native to Central Asia.
Lythrum salicaria is native to Europe, temperate Asia, northern Africa, and Australia. It is also naturalised in many temperate regions around the world, including parts of southern Africa, North America, and South America. It was long thought to be a recent introduction to Australia, but pre-colonial pollen samples have been found in New South Wales, indicating natural colonisation occurred before modern human plant introductions; Australian authorities consider this question unresolved.
This species grows in ditches, wet meadows, and marshes, and along the edges of lakes. In North America, it can invade sedge meadows.
It has been used as an astringent medicinal herb to treat diarrhea and dysentery, and is considered safe for use by all age groups, including babies. It is also grown as an ornamental plant in gardens, and is particularly associated with damp, poorly drained locations such as marshes, bogs, and watersides, though it can tolerate drier conditions. Its flowers are showy and bright, and a number of cultivars have been selected for variation in flower colour: 'Atropurpureum' with dark purple flowers, 'Brightness' with deep pink flowers, 'Happy' with red flowers on a short (60 cm or 24 in) stem, 'Purple Spires' with purple flowers on a tall stem, and 'Roseum Superbum' with large pink flowers. The cultivars 'Blush' with blush-pink flowers and 'Feuerkerze' with rose-red flowers have received the Royal Horticultural Society's Award of Garden Merit. It has also been introduced to many areas of North America by beekeepers, because its abundant flowers provide an important source of nectar.
