Fanwort has been in Cullaby Lake, on the north coast of Oregon, for at least 10 years where it creates severe nuisance conditions. Fanwort is a serious aquatic weed as far north as upstate New York and Michigan. It clearly has the ability to grow and create serious weed problems in Washington. Like many problem aquatic plants, fanwort can regenerate from small stem fragments. Fanwort stems become brittle in late summer, which causes the plant to break apart, facilitating distribution and invasion of new water bodies.
Fanwort is self-pollinating in the South and seeds readily germinate.
Yet, seeds collected in New Jersey failed to germinate. There is no information on seed viability in the Northwest. There has been little research on fanwort biology or management. There are reports that fanwort is less sensitive to the herbicides available for management in Washington than other aquatic plants. Drawdown has been used to reduce fanwort growth in the South, however, extreme drying is necessary to prevent regrowth from seeds.