This subaquatic weed originates from subtropical to warm temperate regions of southeast Asia, where it is often associated with traditional cultivation of rice in paddy fields on terraces (Cruz-Garcia & Price 2011, Hong et al. 2019). The species has become locally invasive in similar riparian or wetland habitats across the World. It is cultivated occasionally in North America, sold in oriental food markets, and featured in a recent movie "Minari" (2020 Sundance Film Festical). In the eastern USA, naturlized plants were first recorded in Mo. during the 1980s (SERNEC 2024) and have now spread across east-central states (K). It was first recorded in Ohio in 2018 (Becus & Vincent 2020). V. Voelker found it in FAYE (with colls. for EKY) during 2024, and there are records from suburban areas in other counties during 2022-23 on iNaturalist. Some patches already cover 100s of square meters, especially on muddy streambanks. However, the species appears to be excluded in more shady unmowed riparian zones. O. javanica has had much medicinal and culinary use in East Asia (Lu & Li 2019, Murata et al. 2021). Wikipedia (2024) states: "While many other species of Oenanthe are extremely toxic, Oenanthe javanica is edible, and is cultivated in China, India, Japan, Korea, Indonesia, Malaysia, Thailand, Taiwan, and Vietnam, as well as in Italy, where its spring growths are relished as a vegetable." Its complex chemistry includes an unusual sulphated flavonoid, "persicarin" (Ku et al. 2013)--which has also been found in Anethum graveolens (dill) and Persicaria hydropiper (water pepper). After their review, Lu & Li (2019) urged some caution: "Furthermore, a subchronic toxicology of O. javanica at high dose (equivalent to 20 times the recommended human clinical dose) was observed in rats, but the potential toxic component and its possible mechanism have not been revealed... In addition, a rare case of irritant contact dermatitis owing to O. javanica was reported."