Duck-lettuce is an annual, submersed aquatic plant native to the rice fields of southeastern Asia, but has naturalized to Louisiana, California, and more recently Missouri and Florida. It reproduces solely by seeds, is slow to spread, and is generally not considered a top invasive plant in the United States. It is, however, a Federally Listed Noxious Weed.
Ottelia alismoides was first found in Florida in 2003. The duck-lettuce was growing in Thompsons Bayou, a small, slow-flowing tributary of the Escambia River. The infestation contained several plants along the shoreline adjacent to the University of West Florida campus and appeared to be intentionally planted. A systematic survey conducted later in the year found less than one patchy acre of duck-lettuce in the tributary. Biologists removed as many specimens as possible, but complete eradication may be impossible. The tributary is home to a diversity of native plant species, including Echinodorus cordifolia, Orontium aquaticum, and Potamogeton pulcher, and widespread eradication of Ottelia alismoides may cause more harm to the preserve. Due to the increased salinity of the river a few miles downstream, Ottelia will have a hard time spreading. The USDA and DEP are continuing to monitor the growth of duck-lettuce to determine whether or not it will become an invasive species in Florida.
Information provided by Jess Van Dyke / Bureau of Invasive Plant Management, Florida DEP and US Department of Agriculture.