Native herb of Brazil and Argentina. Invasive in Australia, China, New Zealand,Thailand and USA. In 1995 it was found that Alligator weed has been growing in home gardens of the Sri Lankan community in Australia as a vegetable by mistake*. Later on somehow it was introduced to the Sri Lanka and now an invasive weed in several areas, growing in dense masses in shallow water.
* Invasive Plants - A guide to the identification of the most invasive plants in Sri Lanka, Lalith Gunasekara