Factors Influencing the Planting Success of Justicia americana (L.) Vahl (American Water Willow) in a State Scenic River in Ohio

To address the dearth of information on Justicia americana (American Water Willow) establishment and occurrence in rivers, we conducted a 4-year study in 2 Ohio state scenic rivers to evaluate the factors influencing planting success. We surveyed 1 river with extensive American Water Willow colonies and then planted American Water Willow at 15 sites in another river largely devoid of American Water Willow colonies. We also compared hydrologic regimes between the 2 rivers. Percent occurrence of planted individuals was greatest in sites receiving 1 early spring planting of dormant individuals and 2 summer plantings of non-dormant individuals. Percent survival differed only in 2021 and was greatest in sites receiving 1 early spring planting of dormant individuals and 2 summer plantings of non-dormant individuals. Greater percent survival was associated with cobble-dominated substrate compared to clay-, sand-, or gravel-dominated substrates. Colony survival and flooding frequency were greater in the river with extensive existing colonies than in the river with few existing colonies and greater flooding intensity. Our results suggest that the establishment and growth of American Water Willow are influenced by planting method, substrate type, and flooding intensity.