History It is believed that the water hyacinth was introduced first into the United States at the World's Industrial and Cotton Centennial Exposition of 1884-1885 in Louisiana. A Florida visitor to the Exposition apparently returned home with water hyacinth plants and subsequently released them into the St. Johns River. From there water hyacinth plants rapidly spread to neighboring states. These plants slowly increase in number and size during the spring and summer until the maximum biomass is reached in September. As the plants become crowded, many of the lower leaves die back due to shading.
Water hyacinths are in full bloom in late summer and early fall.
Seeds form in the submerged, withered flower. By late fall some of the old leaves start dying and by January most plants have senescensed. Colonization of a new site begins with small plants at low plant densities. These plants increase in number and density without increasing in size until they produce a new mat. As a mature dense mat is formed, individual plant size continues to increase, but density decreases as the result of intraspecific competition.