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Yellow floating heart is a perennial, water lily-like plant that carpets the water surface with long-stalked heart-shaped leaves. The showy five-petaled yellow flowers occur on long stalks and rise a few inches above the water. Yellow floating heart is a native of Eurasia and the Mediterranean area as well as Japan, China, and India and has been introduced into Washington, particularly along the Spokane River near Spokane. We speculate that nurseries sold yellow floating heart as an ornamental water plant because of its attractive yellow flowers and floating leaves. The Washington State Noxious Weed Control Board listed yellow floating heart as a Class B noxious weed in 2001. The Washington Department of Agriculture prohibits its sale, trade, and transport in Washington.
Like other floating leaved plants, yellow floating heart grows in dense patches, excluding native species and creating stagnant areas with low oxygen levels underneath the floating mats. These mats make it difficult for folks to fish, water ski, swim, or even paddle a canoe. Yellow floating heart prefers slow moving rivers, lakes, reservoirs, and ponds. Yellow floating heart reproduces by water-dispersed seeds and by new stolens. Broken off leaves with part of a stem will also form new plants.
There is a wide-spread infestation of yellow floating heart in Lake Spokane in Stevens County (eastern Washington). Whatcom County Weed Board discovered several small infestations in Whatcom County (northwest Washington) and there is a small infestation in Yakima County.
We have had little direct experience controlling yellow floating heart in Washington. However, yellow floating heart has a similar growth habit to the fragrant water lily and plant managers expect that methods used to manage fragrant water lilies will be effective on yellow floating heart. Plant managers control fragrant water lilies by cutting, harvesting, covering with bottom barrier materials, and aquatic herbicides (Rodeo®). Grass carp do not eat water lilies in Washington and it is not known if they would readily eat yellow floating heart.
Look for the following characteristics
Don't confuse yellow floating heart with Washington’s native spatterdock (also called yellow pond or cow lily) which has a yellow ball-shaped flowers and large elephant-ear-shaped leaves. Another native look-alike plant, watershield, has small floating leaves with the underside often coated in a gelatinous slime. Watershield has inconspicuous purple flowers. Aquatic plants nurseries may also sell other ornamental species of Nymphoides sp. and these may be confused with yellow floating heart. Contact your county weed board for positive identification.
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