Factors influencing the planting success of Justicia americana (L.) Vahl (American Water Willow) in a state scenic river in Ohio

Authors: BRUBAKER, GRACE - Mount Vernon Nazarene University; Smiley, Peter - Rocky; BOSSLEY, JON - Mount Vernon Nazarene University

Submitted to: Northeastern Naturalist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2023
Publication Date: 11/27/2023
Citation: Brubaker, G., Smiley, P.C., Bossley, J.P. 2023. Factors influencing the planting success of Justicia americana (L.) Vahl (American Water Willow) in a state scenic river in Ohio. Northeastern Naturalist. 30(4):407-428. https://doi.org/10.1656/045.030.0405.
DOI: https://doi.org/10.1656/045.030.0405

Interpretive Summary: American water willow is a common emergent aquatic plant species found in streams and rivers in the eastern United States that provides habitat for aquatic animals, promotes substrate stability, and uptakes nutrients. Information is lacking on the environmental variables that promote the colonization and growth of this native aquatic plant in rivers and whether it is feasible to plant this species as part of stream restoration efforts. We conducted a four year field study to evaluate the factors influencing American water willow colonization and growth in two state scenic rivers in central Ohio. We found that survival of planted American water willow was greater in sites that received three plantings and sites with cobble substrate. We also documented that American water willow survival and flooding frequency were greater in the state scenic river that exhibited the greatest abundance of American water willow. Our results indicated that the growth and colonization of American Water Willow was influenced by planting methods, substrate type, and flooding intensity. Our results represent the first documentation of the feasibility of planting American water willow in streams and rivers in the Midwestern United States and of this aquatic plant’s preference for cobble substrate. Our results indicate that it is feasible to plant this aquatic plant in agricultural rivers with predominately gravel and cobble substrate in the Midwestern United States as part of stream restoration efforts. Our results will assist state agencies, federal agencies, non-profit groups, and consulting agencies involved with conservation and management of aquatic plants in lentic and lotic ecosystems within agricultural watersheds.

Technical Abstract: Information is lacking on the factors that influence colonization and growth of Justicia americana (American Water Willow) in rivers throughout the eastern United States. We conducted a four year field study to evaluate the factors influencing American Water Willow colonization and growth in an Ohio state scenic river that exhibited a low American Water Willow abundance. Percent occurrence of planted American Water Willow survivors was greater in sites receiving three plantings, than sites receiving one or two plantings. Percent survival differed only in 2021 and was the greatest in sites receiving three plantings. Greater percent survival was also associated with cobble substrate. Colony survival and flooding frequency were greater in a state scenic river having a high American Water Willow abundance than the state scenic river that exhibited a low abundance. Our results suggest the growth and colonization of American Water Willow is influenced by planting methods, substrate type, and flooding intensity.