prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses

prolific South American aquatic weed having grasslike leaves and short spikes of white flowers; clogs waterways with dense floating masses