Erect stems are produced prior to flowering, growing to a height of 1.5m or more. In fertile situations its growth rate can exceed 15cm a week. It forms dense floating mats which can quickly cover waterbodies, excluding other life forms as well as impeding water flow, navigation and recreational activities. Problems with flooding due to impedance by this plant have already occurred in New Zealand. Stem fragments may be spread by water movement, deliberate plantings or by drainage machinery.
Fragments quickly develop roots and new stems when they come to rest, forming new colonies.
Dispersal of seed is by water movement, or mud sticking to animals or machinery. Attempts to clear sites mechanically should be carried out with caution in order not to spread fragments of the plant down stream or to contaminate machinery. Disposal Bury deeply underground away from watercourses.