Purple loosestrife has taken over waterways across the United States, invading wet areas such as lakeshores, stream banks, marshes, ditches, and canals. Purple loosestrife spreads uncontrolled in North America because it escaped its specialized insects and diseases that kept it in check in its native lands. One plant can produce up to 2.7 million seeds, allowing the plant to spread quickly.
Purple loosestrife invades a Northern California lake.