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Origin
Lythrum salicaria was introduced from Eurasia in the 1800s as an ornamental. Its first appearance was recorded in the estuaries of northeastern North America.
Known Distribution
Purple Loosestrife is reported by the USDA to occur in 42 of the 48 contiguous states. Although the plant can still be found in some nurseries it is listed as a noxious weed in many states, including Missouri, and as an exotic weed in Illinois. In these places it is illegal to sell the plant.
Habitat
This dangerous beauty invades many wetlands including freshwater meadows, tidal and non tidal marshes, river and stream banks, pond edges, reservoirs and ditches.
Ecology
Purple Loosestrife provides little nourishment or value to wildlife. It quickly replaces native plant species by forming a homogenous stand. The establishment of this invasive in a habitat will drastically reduce local diversity.
Identification
This herbaceous plant is in the loosestrife family (Lythraceae). The plant grows erect and can reach from 4 to 10 feet high with a woody stem usually covered in downy hairs.
Leaves appear lance shaped, stalk-less and rounded to heart-shaped at the base. They are arranged in pairs or whorls around stem.
Flowers, fruits and seeds: This loosestrife produces magenta colored flower spikes throughout summer, with 5 to 7 petals per individual flower. A single mature plant may contain 30 to 50 stems and can produce 2 to 3 million seeds per year. Flowers require pollination by insects.
Dispersal: Purple Loosestrife produces a vast quantity of seeds which are dispersed by wind and water. The plant is also capable of reproducing vegetatively through underground stems at a rate of 1 foot per year.
Prevention and Control
Small plants may be pulled by hand, taking care to extract all roots from the ground. Older populations may require herbicides such as Rodeo®, for wetlands or near water, and Roundup®, for upland populations. Biological controls, such as several species of imported beetles approved by the USDA, are also available.
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