Hydrilla is probably the most troublesome submersed aquatic plant in North America. It grows rapidly under very low light levels, in a variety of aquatic habitats from static to flowing water and at depths from an inch to 50 feet. The stem branches in the upper parts of the water column, forming a canopy that inhibits growth of native species and interferes with recreational use of lakes. Stem fragments are formed by harvesting operations and by boat props. Each stem piece can root and form a new plant.
Tubers form on the roots in the sediment, and turions form on the stem in the water column.
Tubers are produced in the sediment by the thousands, and sprout in the spring. Turions are smaller and are easily carried by water currents, providing a mechanism for long distance transport. Some strains of Hydrilla can set very small seeds. Hydrilla is found in one lake system in western Washington where an eradication program has been underway since 1995. Tubers and turions complicate control strategies.