Cabomba caroliniana

Fanwort

NOT NATIVE TO MAINE - INVASIVE

Habitat: Fanwort is found in the submersed and floating-leaved plant communities, growing in a variety of substrates including sand, mud and gravel. It thrives in stagnant or slow moving waters of lakes, pond and streams in depths of up to 2.5 meters. Large mats of drifting fragments may occur.

Description: Fanwort is a submersed perennial with stems emerging at intervals along horizontal rhizomes. The plant has two distinct leaf types. The submersed leaves are finely divided, widely branched, and held apart from the stem on slender petioles, resembling tiny fans with handles. The leaves are arranged in opposite pairs along the main stem. The orderly formation of leaves and stems gives the plant a “tubular” appearance underwater. Plants range in color from grass green to olive green to reddish. Floating leaves, when present, are inconspicuous (1 cm long), elongate and elliptical. They are arranged alternately on slender petioles attached to center of each leaf. Small white flowers (1 cm in diameter) develop among the floating leaves.

Origin and Range: Fanwort is native to Europe and parts of the southeastern U.S. It is not native to New England. An attractive plant, fanwort has long been popular in the aquaria trade. Release from aquaria into the environment is considered to be one of the means by which this plant has spread beyond it natural range. Fanwort occurs, and is considered invasive, in many parts of the US including the nearby states of New Hampshire, Massachusetts, New York, and Rhode Island.

Annual Cycle: New shoots emerge from horizontal rhizomes in the spring and grow rapidly to the surface where they can form dense mats. Fanwort blooms from May to September, its small white flowers floating at the surface among a group of tiny floating leaves. Both the rhizomes and the stems are easily broken as the season progresses, facilitating vegetative spread to new areas. Fanwort breaks apart in the late fall and fragments may over-winter, growing into new plants the following season. Although fanwort is self-pollinating, seed germination in areas beyond its natural range does not appear to be significant. Reproduction occurs primarily by regeneration of stem fragments and rhizomes.

Impacts: Under favorable environmental conditions, fanwort can form dense stands, crowding out beneficial native plants and interfering with navigation and traditional recreational uses.

Look Alikes: May be confused with all water milfoil species, common bladderwort, water marigold, white water crowfoot, yellow water crowfoot, coontail, prickly hornwort, and mermaid-weed.