Most aquatic flowering plants spread via specialized vegetative propagules. Such propagules do not occur in Riverweeds (Podostemaceae), which constitute the largest family of strictly aquatic flowering plants. This study was undertaken to test whether root fragments of Podostemum ceratophyllum Michx. (Hornleaf Riverweed) can reattach and thereby serve a dispersal role. In field experiments, root fragments re-attached with tenacity sufficient to challenge removal. We conclude that fragments can provide a vegetative means to disperse plants in rivers. While the plant tested is the only species of the family in North America, the results have broader implications for the largely tropical Podostemaceae.