South and Central America as well as southeastern United States.
Fanwort is a submersed, sometimes floating, but often rooted, freshwater perennial plant with short, fragile rhizomes. The erect shoots are upturned extensions of the horizontal rhizomes. The shoots are grass green to olive green or sometimes reddish brown. The leaves are of 2 types: submersed and floating. The submersed leaves are finely divided and arranged in pairs on the stem, fanning out, thus given their name.
The floating leaves, when present, are linear and inconspicuous, with an alternate arrangement. Flowers are solitary, small, and white with 3 petals and 3 sepals. This species grows rooted in the mud of stagnant to slow-flowing water, including streams, smaller rivers, lakes, ponds, sloughs, and ditches.
People often use this plant in their home aquariums and dispose of it in a natural area. This plant can spread by seed and also by rhizomes as well as by attaching itself to boats and water fowl. It is able to survive under the winter ice layer.
Fanwort forms dense stands, choking out native plants species by changing and heating water temperatures (thus limiting fish species) if the stands that are formed are dense enough. Similarly to milfoil, it easily invades different waterways by not needing a root system to grow.
Fanwort, like milfoil, is best controlled in waterways by means of large harvesting equipment to catch and dispose of the plant. For very small areas, rakes can be useful in removing the plant. Water level adjustment and chemical treatment are also possible methods of control, but require further study of the waterway to assess impact. Please be sure to inspect your canoe, kayak, or boat before leaving a site to prevent spreading this invasive plant to other waterbodies. Washing or rinsing the underside at the site is recommended. Any removal within 100 feet of wetland resource areas, including certified vernal pools, or within 200 feet of a perennial stream may require approval from the Concord Natural Resources Commission. Please contact the Division of Natural Resources before you begin.
The following native plants can serve as a good replacement to Fanwort: