Description:
Purple Loosestrife is a perennial with erect square stems up to eight feet tall. It grows in moist or marshy area. Purple Loosestrife spreads by seed and rhizome roots. The plant produces rose-purple flowers wiht five to seven petals. The leaves are long and narrow, and are arranged opposite on the stems.
 

• Mechanical: Small infestations of Purple loosestrife can be removed prior to seed production by hand pulling. Digging is recommended for mature plants, being sure to remove all of the root. The plant will re-sprout from root parts left behind. Always bag and destroy all plant material. Cutting and destroyinge flower heads will prevent seed production.
• Biological: Two leaf beetles and a root weevil have been introduced.
• Herbicide: Do not use herbicides in wetland or aquatic areas without first calling your local Weed Control Agency. Refer to the State Noxious Weed Control Board site

For More Information:
Detailed information about Purple Loosestrife is available at the Washington State Noxious Weed Control Board Web Site.