Several plants could claim this title, but the world’s worst y water weed is undoubtedly the water hyacinth. Found in 50 countries on five continents, this free-floating South American plant can double in mass every five days.
It forms dense mats which rapidly clog waterways, limit boat traffic and stop sunlight and oxygen reaching underwater. 50 million tons of water hyacinth are removed each year from the White Nile alone. This exotic plant can escape into the wild from ornamental ponds where it is prized for its beautiful purple-blue flowers and attractive shiny dark-green leaves.