Submersed Plants

Species: Cabomba caroliniana Gray, fanwort
Family: Cobombaceae

Fanwort has fan-shaped, deep green or reddish, delicately divided, opposite underwater leaves. Most of the plant is underwater, but oblong floating leaves sometimes occur on the water surface, usually when the plant is flowering. Fanwort is commonly sold as an aquarium plant (it is now illegal to sell this plant in Washington) and is not native to Washington, although it has been introduced to a slough off the Columbia River in southwestern Washington and is found in coastal Oregon lakes.

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Leaf: Two types–submersed and floating. Fan-shaped submersed leaves are opposite, up to 6 cm across, and finely-divided on leaf stalks up to 3 cm long. Floating leaves usually develop when the plant is flowering and are alternate, narrowly diamond or arrowhead shaped, and up to 2 cm long with centrally attached leaf stalks.

Stem: Up to 2 m long, slender, and sometimes covered with gelatinous slime. 

Flower: Approximately 1-2 cm across with 3 white petals and 3 similar looking sepals. The 3 petals are yellow near the base. The yellow color directs insect pollinators to the nectaries. Flower stalks originate at the base of the upper leaves.

Fruit: 2-4 leathery pods per flower; each 2-3 cm long and 1 mm wide, usually containing 3 seeds each.

Root: Long and thin. Plants usually rooted in the sediments, but can continue to grow if uprooted.

Propagation: Seeds, rhizomes, and stem fragments.

Importance of plant: When introduced to water outside its native southeastern United States its dense growth can reach nuisance proportions. It is even known as a nuisance plant within its native range.

Distribution: Primarily eastern U.S., but has been found in southwestern Washington and in Oregon coastal lakes. Probably introduced to the Northwest by improper disposal of aquarium plants.

Habitat: Favors ponds, lakes, and quiet streams with low pH. Commonly roots in 1-3 m of water. 

May be confused with: Other submersed plants with finely divided leaves such as white water-buttercup (Ranunculas sp.), which has alternate leaves; water-marigold (Megalodonta beckii) which has leaves on short stalks; coontails (Ceratophyllum spp.), which lack roots and have whorled leaves; or the water-milfoils (Myriophyllum spp.), which have whorled, feather-shaped leaves.

Photographs: Closeup of Cabomba caroliniana plants

Line Drawings: Cabomba caroliniana

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