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Plant Invaders of Mid-Atlantic Natural Areas

Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of
Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

Purple Loosestrife
Britt Slattery, USFWS
Purple Loosestrife
Lythrum salicaria

Origin: Eurasia

Purple loosestrife was introduced to the northeastern United States and Canada in the 1800s for ornamental and medicinal uses. It is still widely sold as an ornamental, except in states such as Minnesota, Wisconsin and Illinois where regulations now prohibit its sale, purchase and distribution. Purple loosestrife adapts readily to natural and disturbed wetlands.

Distribution and Ecological Threat
According to the U.S. Fish and Wildlife Service, purple loosestrife now occurs in every state except Florida. Purple loosestrife is capable of invading many wetlands, including wet freshwater meadows, tidal and non-tidal marshes, river and stream banks, pond edges, reservoirs and ditches. Under favorable conditions, loosestrife is able to rapidly establish and replace native vegetation with a dense, homogeneous stand that reduces local biodiversity, endangers rare species and provides little value to wildlife.

Description and Biology

  • Plant: erect perennial herb in the loosestrife family (Lythraceae); have a square, woody stem usually covered by downy hair; grow from 4 to 10 feet high, depending upon conditions.
  • Leaves: lance-shaped, stalk-less and rounded to heart-shaped at the base; arranged in pairs or whorls around the stem.
  • Flowers, fruits and seeds: produces a showy display of magenta-colored flower spikes throughout much of the summer. Individual flowers have five to seven petals. A single mature plant can have 30 to 50 stems arising from one rootstock, and can produce an estimated two to three million seeds per year. The flowering season extends from June to September; flowers require pollination by insects, for which they supply an abundant source of nectar.
  • Spreads: through the vast quantity of seeds, dispersed by wind and water. It also readily reproduces vegetatively through underground stems at a rate of about one foot per year.

Prevention and Control
Small infestations of young purple loosestrife plants may be pulled by hand, preferably before seed set. For older plants, spot treatment with a glyphosate type herbicide (Rodeo® for wetlands or near water, Roundup® for uplands) may be effective. Biological control, using several imported beetle species approved by the USDA for release, is the most effective method for long-term control of large infestations. Although these beetles occasionally feed on native plant species, their potential impact to non-target plants is considered to be minimal.

Native Alternatives

Joe Pye weed (Eupatorium fistulosum)
Joe Pye Weed
Chris Miller, NRCS
cardinal flower (Lobelia cardinalis)
Cardinal Flower
blue vervain (Verbena hastata)
Blue Vervain
R. Harrison Wiegand

blazing star or gayfeather (Liatris spicata)
Blazing Star or Gayfeather
Randy Loftus, USFWS
New York ironweed (Vernonia noveboracensis)
New York Ironweed
Britt Slattery, USFWS
obedient plant
(Physostegia virginiana)
Obedient Plant
Britt Slattery, USFWS

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USDA Forest ServiceUSDA APHIS PPQ The Bugwood Network University of Georgia is a joint project of
The Bugwood Network, USDA Forest Service & USDA APHIS PPQ.
The University of Georgia - Warnell School of Forest Resources and
College of Agricultural and Environmental Sciences - Dept. of Entomology
Last updated on Wednesday, November 05, 2003 at 01:26 PM
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