Hydrilla

Hydrilla (Hydrilla verticillata), also commonly called water thyme, is a submersed perennial herb. The plant is rooted in the bed of the waterbody and has long stems (up to 25 feet in length) that branch at the surface where growth becomes horizontal and forms dense mats. Small (2 – 4 mm wide, 6 – 20 mm long), pointed, often serrated leaves are arranged around the stem in whorls of 3 to 10.