Parsley Water-dropwort (Oenanthe lachenalii).
Near Threatened on @BSBIbotany's #EnglandRedList, it's rare in Oxon, but is thriving here in the Lye Valley, with 100s of plants. Our entry for @wildflower_hour's #WetlandPlants on #BogDay2021.
@judyweb32049878 @Blysmus