Why are some Cyperus, Fimbristylis, and Schoenoplectus species weeds in rice paddies?

Species of Cyperus, Fimbristylis, and Schoenoplectus are significant weeds in rice paddies primarily because they are well-adapted to the specific ecological conditions of these wetlands.1

Many sedges are naturally suited to sunny, moist-to-wet habitats, and these genera are particularly noted for their role as early colonizers on bare, wet soil. Because rice cultivation—especially in Asia—requires the inundation of fields with water for much of the growing season, these sedges find an ideal environment to thrive alongside the crop.213

Furthermore, these plants often persist in the environment through a seedbank, where dormant, viable seeds remain in the soil during dry periods and germinate when conditions become appropriate, such as when a paddy is flooded. Their ability to rapidly colonize newly created or disturbed wet habitats allows them to compete effectively in cultivated sites where the original vegetation has been removed.1