florida Early Detection Network


Purple loosestrife


Lythrum salicaria L.


Loosestrife family


Lythrum salicaria




Inflorescence close-up


Inflorescence Close-up


Synonyms: None


Botanical Glossary

Lythrum salicaria is an herbaceous wetland perennial that can grow 0.5-1.5 m (1.5-5 ft.) tall. The leaves are either opposite or in whorls of three. The can be pubescent or glabrous. They are lanceolate to linear in shape and 3-10 cm (1-4 in.) long. The larger leaves can be cordate or clasping at their bases. The flowers are purple, magenta or pink. They are numerous and borne on spikes that are between 10 and 40 cm (4-16 in.) long. The hypanthium is linear and twice as long as the sepals. Each flower has 5-7 petals, and the open flowers measure 7-12 mm (0.3-0.5 in.) in diameter. The relative lengths of styles and stamen in these flowers can vary in three different ways. The flowers are in bloom from July to September. The fruits are capsules, each containing numerous reddish-brown seeds. Page References Bailey 719, Crow & Hellquist 203, Fernald 1048, Gleason & Cronquist 311, Holmgren 292, Magee & Ahles 758, Newcomb 351, Peterson & McKenny 224,288. See reference section below for full citations.


Lythrum alatum Pursch. (winged loosestrife)* Picture of L. alatum. Lythrum alatum is a rare plant that could be confused for L. salicaria. Lythrum alatum is usually shorter in stature, being around 40-80 cm (1-2.5 ft.) tall. The leaves of L. alatum are alternately arranged, except for the very lowest ones on the plant. The flowers of L. alatum are solitary in the upper axils while the flowers of L. salicaria are numerous and in a spike-like arrangement.


Lythrum salicaria reproduces through prolific seed dispersal. The seeds usually fall to the ground after they have ripened. They can be moved longer distances by water or by becoming attached to waterfowl.


The native distribution of Lythrum salicaria is central and southern Europe, Great Britain, and parts of Russia. It has been reported from every state in the United States except for Florida, Arizona, Louisiana, Georgia, Alaska and Hawaii. This plant occurs widely in New England.


The first report of Lythrum salicaria in North America was in 1814. Before the year 1900, 14 of 30 populations of this plant were located in estuaries from Massachusetts to New Jersey. The location of these sites would indicate that the plant was introduced somewhere in this area. There are several hypotheses on how this plant was originally introduced. It could have been a part of ship ballast from Europe, or attached to sheep. Lythrum salicaria was also planted as a source of nectar for beekeeping, as an ornamental, and for medicinal reasons. By the 1900's there were more inland populations being reported, one of these being in New Hampshire. Since these initial introductions it has spread by being planted in gardens and by waterways.


Coastal Grassland, Herbaceous Wetland, Lake or Pond, River or Stream, Shrub Wetland, Wet Meadow, Yard or Garden. Lythrum salicaria is most often found in situations where the soil is moist. However, it prefers areas with shallow water, and does not grow as prolifically in deep-water situations.


Lythrum salicaria has the ability to completely dominate wetlands, forming a vast, monotypic stands. These stands prevent the establishment of native wetland plants. It can also have an effect on native wildlife that may not be able to use the plants as effectively for food or cover. By forming these dense stands, Lythrum salicaria can clog waterways, causing problems for both commercial and recreational uses of these areas. Lythrum salicaria can produce up to 2.5 million seeds per plant. Thes seeds persist in the seed bank for years, even if the plants themselves are eradicated from an area. This plant can hybridize with a native loosestrife, L. alatum, which is considered rare in Connecticut. With repeated hybridizations, it is possible that the gene pool for L. alatum could be depleted.


The Nature Conservancy

Wisconsin Department of Natural Resources

The Connecticut Invasive Plant Working Group Invasive Plant Management Guide

Plant Conservation Alliance Fact sheet with management information


Documentation required: A photograph of the plant habit, flowers or fruit. Best time for documentation: Summer, fall.


Integrated Taxonomic Information System Has general taxonomic information about the species.

The PLANTS database General information and a map

The Nature Conservancy Extensive description, biology, photographs and control information

Plant Conservation Alliance Fact sheet that includes images and control information

Ohio Perennial and Biennial Weed Guide Photographs and description

Wisconsin Department of Natural Resources Description, biology and control information

National Invasive Species Information Center Links to more information

Illinois Nature Preserves Commission General information and control

Adirondack Park Invasive Plant Program Identification, fact sheet, management and distribution information


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