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Purple Loosestrife

Purple Loosestrife

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Purple Loosestrife

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  1. Purple Loosestrife

  2. Scientific Classification • Kingdom: Plantae • Division: Magnoliophyta • Class: Magnoliopsida • Order: Myrtales • Family: Lythraceae • Genus: Lythrum • Species: Lythrumsalicaria

  3. Description • Erect perennial herb of the loosestrife family, with a square, woody stem and opposite or whorled leaves • Leaves are lance-shaped, stalkless, and heart-shaped or rounded at the base • Loosestrife plants grow from two to seven feet high, depending upon conditions, and produce a showy display of magenta-colored flower spikes throughout much of the summer • Flowers have five to seven petals. • Mature plants can have from 30 to 50 stems arising from a single rootstock

  4. Preferred Habitat • Purple loosestrife is capable of invading many wetland types, including freshwater wet meadows, tidal and non-tidal marshes, river and stream banks, pond edges, reservoirs, and ditches. 

  5. Purple loosestrife is found in every state except Florida, but is not reported invasive everywhere.

  6. Cultivation and Uses • Purple loosestrife has been used as a medicinal herb to treat diarrhea and dysentery; it is considered safe to use for all ages, including babies. • It is also cultivated as an ornamental plant in gardens. The flowers are showy and bright, and a number of cultivars have been selected for variation in flower color

  7. A Beautiful Disaster • Around 1800, purple loosestrife was transported to North America on soil ballast from Europe, arriving in New Jersey, New York, and New England • Between 1800 and 1850, the weed established itself over a limited coastal area in the Eastern U.S. • The spread was slow at first, moving with water currents and floods • Gardeners also spread purple loosestrife, but to a lesser extent

  8. By 1900, purple loosestrife had reached Chicago, and a few decades later the Mississippi River • By 1940, most of the northeastern and north-central U.S. was infested, and long-distance transport established purple loosestrife in Washington State

  9. In the 1950s and 1960s, it became increasingly more apparent that purple loosestrife was hindering wetland production and wildlife • By the 1970s, several projects began working towards identifying the plant as an invasive • A 1987 report by Dan Thompson brought purple loosestrife’s negative impacts to light by quantifying the amounts of cattail habitat loss and muskrat decline in areas of infestation

  10. Biology and Spread • Purple loosestrife’s flowering season is from June until September • It is rich in nectar content, and many insects pollinate the plant • One mature plant can have as many as thirty flowering stems capable of producing two-three million seeds • Spreading at a rate of 115,000 ha/yr

  11. Purple loosestrife is capable of reproducing at one foot per year with underground stems • Even purple loosestrife cultivated as “guaranteed sterile” is still capable of reproducing with other purple loosestrife (in some cases other plants in the genera Lythrum)

  12. Ecological Threats • Being an invasive, purple loosestrife adapts easily to natural and disturbed wetlands. • As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality source of nutrition for wildlife. • The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species, including some federally endangered orchids, and reduce habitat for waterfowl. eastern prarie fringed orchid, Platanthera leucophaea

  13. Herbicides and Human Control • Small patches of purple loosestrife can be pulled physically by hand, preferably before its seeding stage • Older plants can be spot treated with herbicides (Rodeo® for wetlands, Roundup® for uplands) • Multiple treatments are preferred, in late season when the plant prepares for dormancy, as well as mid-summer

  14. Biological Controls • Competition and natural enemies ideally are the best ways to combat purple loosestrife, and other invasives • Currently, four host specific insect species are being used to try to control purple loosestrife • The goal is long-term control and not complete eradication

  15. Hylobius transversovittatus, a root-boring weevil Galerucella calmariensis, a leaf-eating beetle Galerucella pusilla, a leaf-eating beetle Nanophyes marmoratus, a flower-feeding weevil

  16. Economic Damage • Purple loosestrife does not cause direct economic damage, though has some indirect effects • Purple loosestrife causes reduced palatability (a measure of taste) in hay, as well as being responsible for reduced water flow in irrigation systems out West • Reductions in waterfowl viewing and hunting opportunities can occur • Costs approximately 45 million/yr in control costs and forage losses (Pimentel 2005)