Hydrilla can be either monoecious or dioecious with both male and female flowers singly
froma spathe (Cook and Lı”nd 1982, Pieterse 1981). Female flowers consist of three whitish
sepals and three translucent petals, are 10-50 mm long, 4-8 mm wide, attached at leaf axils, are
clustered toward the tips of the stems, and float on the water surface. The stem tips from which
female flowers arise are often very compact and have very short leaves. Female flowers are
resistant to wetting and when returned to the water surface after submergence will immediately
re-float. A submerged female flower has been described as an inverted bell filled with a large
bubble. Male flowers have three whitish red or brown sepals that are up to 3 mm long and
2mm wide. They have three whitish or reddish linear petals that are about 2mm long and they
have three stamens which are formed in leaf axils. Male flowers are released and float to the
surface as they approach maturity. Thousands of these free floating male flowers are
sometimes observed in windrows on ponds (Langeland and Schiller, 1983). Both male and
female flowers are produced singly from the spathe.