An Exotic Menace Description. Purple loosestrife flowers from July through August in New Hampshire, and is named for its bright purple flower that spikes from the top of the plant. One plant may grow as an individual stalk or as several stalks clumped together.
Purple loosestrife is native to Eurasia.
It was originally introduced to eastern North America in the early to mid 1800's. This invasive plant was probably accidentally introduced via ship ballast or brought over for use as an ornamental plant. Optimum habitats include freshwater marshes, open stream margins, and alluvial floodplains. Purple loosestrife also occurs in wet meadows, river banks, and edges of ponds and reservoirs. It favors fluctuating water levels and other conditions often associated with disturbed sites, such as construction sites for docks or marinas.