Numerous populations have been found in the Midsouth area. with the heaviest concentrations in the glaciated wetlands of the northeast. The plant now occurs in scattered locations across most of the U.S. Purple loosestrife reached the upper Midwest by the 1930s. The continued expansion proceeded with the development and use of road systems, with commercial distribution of the plant for horticultural purposes, and with regional propagation of seed for bee forage. The range then expanded further inland in the 1880s as the construction of inland canals and waterways increased. For nearly a century it occurred as a pioneer species on the northeastern seaboard. Origin and DistributionPurple loosestrife was introduced to North America from Europe and Asia during the early 1800s as a contaminant of European ship ballasts and as a valued medicinal herb for the treatment of diarrhea, dysentery, bleeding, wounds, ulcers, and sores. Plants thrive under moist soil conditions and in full sun however, they can survive in up to 50% shade. HabitatPurple loosestrife is an aquatic to semiaquatic species occurring in a variety of different shallow water wetlands including marshes, bogs, wet meadows, stream and river banks, shores of lakes and reservoirs, wet pastures, roadside ditches, and disturbed wet soils. In addition, plant fragments produced by muskrats and by mechanical clipping can rapidly spread through river and lake systems. A single, mature plant can produce more than 2.5 million seeds annually. Plants reproduce primarily by seeds, but also by vegetative cuttings. Under natural conditions, seedling densities can approach 12,000-24,000 plants/sq. Each plant has an average of 30 stems which die in late fall but remain standing through winter. New stems emerge from the perennial roots allowing the plant to establish dense stands within a few years. Purple loosestrife has a vigorous rootstock that serves as a storage organ, providing resources for growth in spring and regrowth if the plant has been damaged from cuttings. Also known as Bouquet-violet, it belongs to the Lythraceae (Loosestrife) family. This aggressive invader replaces native vegetation, degrades wildlife habitat, and obstructs natural waterways. Life HistoryPurple loosestrife ( Lythrum salicaria L.) is a wetland perennial that forms large, monotypic stands throughout the temperate regions of the U.S. ImagesPhoto: Linda Wilson, University of Idaho, Seeds are long-lived and can remain viable even after 20 months of submergence in water. Seeds are commonly dispersed by wind, but are also dispersed in water and mud adhering to aquatic wildlife, livestock, and people. Seeds are dispersed from late summer through the winter. Each plant may contain up to 900 capsules. SeedsThe capsules contain an average of 120 orange, minute seeds (0.06 mg). Each plant may bear as many as 3,000 flowers. The self-incompatible, insect-pollinated flowers bloom from June to September and the flower stalks remain standing through the winter. The calyx tube has hirsute lobes 0.02-0.03 inch (0.5-0.8 mm) long which, along with the bracts, are greenish. Three forms of the species are distinguished based on the length of the style (up to 1/4 inch or 7 mm) in the flowers. Leaves are lanceolate and up to 4 inches (10 cm) long and 0.6 inch (1.5 cm) wide with an obtuse or cordate leaf base.įlowersPurple loosestrife has showy, attractive flowers with 5-7 purple petals (occasionally pink or white) occurring in dense, compound, terminal, bracted spikes that may be 6-8 inches (15-20 cm) high. LeavesThe entire, sessile leaves are primarily opposite or in whorls of three without teeth. They may appear woody at base of large plants. StemStems are pubescent and distinctly four-sided. Established plants have 30 to 50 shoots that form wide-topped crowns and dominate the herbaceous canopy. Landscape Alternatives lists native horticultural substitutesĭescription HeightPurple loosestrife grows 3.0-10.0 feet (1-3 m) tall, with an average height of 5 feet (1.5 m). May be confused with the following native and/or non-native species.
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