Water pennyworts are very common. They have long creeping stems that often form dense mats. Water pennyworts occur in and near ponds, lakes, rivers, and marshes. There are seven species and varieties of Hydrocotyle in Florida (Wunderlin, 2003). Water pennyworts can be found throughout the U.S., Canada, and in PR (Kartesz, 1999).
A profusion of leaves and stems is characteristic of water pennyworts. The stems can grow to many feet long. Circular leaves typically are about the size of a half-dollar, but can be much larger or smaller. The leaves are shiny and leathery. The margins have blunted teeth. Long leaf stalks attach at the leaf centers, umbrella-like. Water pennywort flowers form delicate white or greenish umbels.
View the herbarium specimen image from the University of Florida Herbarium Digital Imaging Projects.
For brief control information, see Efficacy of Herbicide Active Ingredients Against Aquatic Weeds by K. Langeland, M. Netherland, and W. Haller.