Method for harvesting and processing water hyacinths, characterized in that the following steps are performed: a) the water hyacinths growing in an aquatic medium are cut; b) the water hyacinths are collected on board a barge at berth (1); c) the collected water hyacinths are transferred onto draining racks (2) near the quayside; d) the drained hyacinths are washed with clean water; e) the washed water hyacinths are drained on vibrating belts (7) in order to remove some of the excess water; f) the water hyacinths are dried on a dryer (8) at a temperature of between 50 and 100° C. for 5 to 17 h; g) the water hyacinths and their seeds are steam-sterilised at a temperature of between 80 and 100° C. in order to sterilise them; h) the sterilised water hyacinths and seeds are ground in order to make profitable use thereof.