Flooding Tolerance of Six Native Landscape Plants for Use in Southeastern Rain Gardens

Abstract

Rain gardens are an effective, attractive, and sustainable stormwater management solution for residential areas and urban green spaces. Although design considerations such as size, susbstrate depth, substrate type, and stormwater holding time have been rigorously tested, little research has been conducted on the living portion of rain gardens. This study subjected six landscape plant species native to southeastern United States to repeated short term flooding to evaluate tolerance to the type of flooding seen in rain gardens. Flooding lasted for 2 d followed by 5 d of no inputs for 7 – 8 wks. Plants were evaluated based on initial and final size index, shoot dry weight, leaf: stem dry weight ratio, stomatal conductance, and leaf chlorophyll content. A diverse set of plants with assorted seasonal benefits was chosen and included two evergreen shrubs (Morella cerifera and Illicium floridanum), two herbaceous perennials (Lobelia cardinalis and Chasmanthium latifolium), and two ferns (Polystichum acrostichoides and Osmunda cinnamomea). Assessment of L. cardinalis was not possible due to extensive damage by herbivorous insects. Damage was not related to flooding and undamaged plants demonstrated the ability to withstand repeated short term flooding. Based on the findings in this research, M. cerifera, C. latifolium, and O. cinnamomea are recommended for use in southeastern rain gardens. P. acrostichoides is not recommended for southeastern rain gardens that do not receive supplemental irrigation during dry periods due to suspected drought intolerance. Future studies are needed to determine if I. floridanum and confirm that L. cardinalis would tolerate short term flooding followed by intermittent dry periods.