Monoecious and dioecious hydrilla grown under greenhouse conditions have been distinguished by differences in leaf and internode length; monoecious plants produced shorter leaves (12.0 ± 2.05 mm) and longer internodes (16.1 ± 1.45 mm) than dioecious plants (14.0 - 16.1 ± 0.82 - 1.45 mm and 11.0 - 12.0 ± 0.82 - 2.05 mm respectively)