Invasiveness of Pongamia, Millettia Pinnata (L.) Panigrahi, in South Florida: an Observational Report

In response to substantial losses in crop production, Florida producers have been seeking alternative species for cultivation. Pongamia (Millettia pinnata / Pongamia pinnata), a fast-growing, subtropical, leguminous tree native to southern Asia, Australia, and the western Pacific islands, has emerged as a potential substitute after a historical period as a landscape ornamental in the region. However, due to its toxicity, prolific production, and ability to disperse long distances along bodies of freshwater, pongamia is considered an environmental weed and was assessed as high invasion risk for Florida in 2016. To examine the establishment status in anticipated escaped populations in south Florida, we surveyed 15 sites with reported occurrences and found established populations at five sites. Among the established populations, we observed clear evidence of rapid spread along the St. Lucie and Cocohatchee rivers, with over 300 recorded individuals of varying sizes and ages across these two sites. These results strongly indicate that pongamia is established in southern Florida and spreading rapidly along freshwater channels. Furthermore, we suspect that poorly managed landscapes such as abandoned nurseries and private horticultural properties have facilitated the observed spread of pongamia. Therefore, we stress the importance of proper management to prevent seed escape from production areas, especially those near bodies of water. Additionally, we highlight the need for expanded surveillance and management for pongamia in Florida.