Leaf margins are serrate, the teeth visible to the naked eye. Fresh leaves are notably rough to the touch. The midrib on the upper surface is often tinged with red and on the lower surface, usually has 1-celled sharp teeth or spines. Male flowers are solitary, small, on short stalks in the leaf axil and break off as buds, opening explosively on the water surface. Leaves mostly in whorls of four at sterile nodes, leaves 1.4 to 2.5 cm long Egeria densa .
Plants grow in canals, springs, streams, ponds, lakes and reservoirs.
Most populations of hydrilla in the United States are dioecious. This species is probably the worst submersed aquatic weed in the United States. In addition to being spread by natural fragmentation, plants are sometimes spread from lake to lake by fragments attached to boat motors and trailers. Cook, C. D. K. and R. Luond. Langeland, K. A. 1996.