Influence of Water Depth on the Rate of Expansion of Giant Cutgrass Populations and Management Implications

Giant cutgrass ( Zizaniopsis miliacea (Michx.) Doell. & Asch.), a tall emergent grass native to the southeastern United States, was studied in Lake Seminole where it formed large expanding stands, and Lake Alice where it was confined to a stable narrow fringe. In Lake Seminole, the production of functional stolons which were able to become rooted in the substrate resulted in stand expansion of 1 to 3 m per year, depending upon water levels. Once flowering stems became decumbent in Lake Alice they were likely to break, with few nodes attached to the parent plant becoming rooted in the substrate, which resulted in a limited rate of stand expansion in Lake Alice. Sections of flowering stems bearing axillary shoots that were detached from the parent plant and freefloating could become rooted on reaching shallow water and produce robust new flowering plants. The reproductive biology of giant cutgrass is well-adapted to promote stand expansion and downstream dispersal, and is related to predicting potential areas of colonization, managing nuisance populations, and the use of giant cutgrass in revegetation projects.