It will also form vegetative propagules called tubers and turions. These propagules are a characteristic unique to hydrilla amongst the Hydrocharitaceae. Turions are compact buds produced in the leaf axils or, in the case of monoecious plants, on stem tips. They break off the parent plant and drift or settle to the bottom to start a new plant. They are 5 - 8 mm long, dark green and appear spiny.
Tubers are underground turions which form at the end of rhizomes.
They are 5 - 10 mm long, and are usually white or yellowish. Both types of hydrilla produce tubers and turions in abundance in the fall as dormant overwintering structures. Tubers may remain dormant yet viable for several years in the sediment, especially in the case of dioecious plants. The monoecious form will also make tubers in the spring and will produce nondormant turions throughout the growing season. The photograph on the right shows the very small tubers produced by the monoecious hydrilla in Washington.