European frog-bit (Hydrocharis morsus-ranae) is a free-floating plant that resembles water lily, though its smaller leaves are distinctly heart-shaped and its flowers are three-rather than multi-petaled. Native to Eurasia, the plant can quickly form dense floating mats in wetlands and other slow-moving water systems.
Frog-bit prefers quiet, show-moving waters and can blanket shallow ponds, marshes and the edges of lakes. Like Eurasian water milfoil, frog-bit can reduce the growth of native submersed aquatic plants and has the potential to impact recreation. Thick mats of frog-bit inhibit light penetration and hinder the movement of fish, waterfowl and boats. Viable plant fragments can spread by to new locations by boaters.
Leaves: thick, heart-shaped, 1 to 2 inches wide and smooth-edged with spongy, purplish-red undersides.
Flowers: small, showy flowers are ½ inch across, appear singly and have three white petals and yellow centers.
Roots: 3 to 8 inches long and unbranched, dangling from the underside of each rosette of leaves.
Reproduction: can spread by sending out stolons which produce ‘daughter’ plants that break free and float to new locations. Also produces turions — compact winter buds that sink to the bottom in fall and float back up in spring to grow into new plants.
Plants can be collected by hand or mechanical harvesters, with all parts composted away from wetlands, rivers, or lakes. Care must be taken to prevent plant fragments from escaping the infestation site. Sites should be checked annually for reinfestations. Use of chemical herbicides also effective.
For more information:
Managing Invasive European Frogbit through Research and Education in New York’s Great Lakes Basin: A Project of the Finger Lakes Institute, Hobart and William Smith Colleges, Cornell University and Cornell Cooperative Extension of Onondaga County