Cut flower spikes before they develop seeds to prevent this year's seeds from producing more plants. Dispose of seed heads in plastic bags. A mature plant can produce over 2.5 million seeds annually. Dig the plant from the ground but take care to remove the entire root system as pieces of root will sprout new plants. This approach works best if there are only a few plants, since purple loosestrife has complex pollination requirements.
Chemical treatment is used when the stands of purple loosestrife are too large for manual control.
Biological controls are now being used in this country to fight purple loosestrife. Five insect species which feed exclusively on purple loosestrife in Europe have been approved for use as biocontrol agents in North America. Beetles are available from N.H. Dept. of Agriculture and VT Dept. of Environmental Conservation. YOU can make a difference . Remove purple loosestrife from your property.