Water conservation practices have become a focal point for many communities because of drought conditions and water restrictions. With increasing urbanization and impervious surface cover, groundwater recharge has decreased (Dietz and Clausen, 2005). Additionally, pumping of groundwater supplies has increased resulting in a need for stormwater management practices that focus on infiltration to maximize groundwater recharge (Dussaillant et al., 2005). When the amount of groundwater pumped exceeds the amount of recharge, aquifers become deficient (Seo et al., 2008). Rain gardens are a homeowner stormwater management practice that can improve groundwater recharge while providing an aesthetically pleasing addition to the landscape.
Non-point source pollution has become a critical issue for both homeowners and agricultural entities in terms of groundwater supplies and water quality (Dietz and Clausen, 2008) with over half of the U.S. population depending on underground sources for potable water (Cabrera, 2005). Impervious surfaces such as concrete increase stormwater runoff. Fertilizers, chemicals, and fecal matter are carried by stormwater runoff to nearby storm drains and ultimately into surface waters, resulting in decreased water quality (Dunnett and Clayden, 2007). The U.S. Environmental Protection Agency (USEPA) reported in 2001 that at least half of the U.S. waters cannot sustain aquatic life because of the presence of excess nutrients (Cabrera, 2005). Rain gardens and bioretention areas are considered best management practices in the collection of stormwater, allowing it to seep into the ground while filtering out harmful pollutants (Dietz and Clausen, 2006; Maryland Department of Environmental Resources, 2007; Shuster et al., 2007; USEPA, 1983).
Residential and commercial landscapes can be designed to effectively manage stormwater and encourage infiltration. A rain garden is a shallow depression that collects and stores stormwater runoff from a roof, parking lot, or any other impervious surface for a short period of time (Dussaillant et al., 2005). Rain gardens use vegetation, soil, and mulch to cycle nutrients and evaporate stormwater. Rain gardens depend on seasonal precipitation as their water source. Therefore, during precipitation events, rain gardens may flood and remain saturated above the substrate level until water permeates the ground. Dussaillant et al. (2005) found that soil in a rain garden would likely remain saturated for 1–2 d and that plant roots should be able to withstand at least 2 d of standing water in the root zone for optimal recharge to occur. This is true for most standard rain gardens in well-drained soils; however, rain gardens sited on clay or clay-loam soils are considered wet rain gardens and may remain flooded for longer than 2 d. Therefore, plants selected for wet rain gardens may need to be tolerant of flooding for longer periods of time due to decreased infiltration rates.
Cyclic flooding has been used to evaluate agricultural crops and wetland species. Cyclic flooding consists of a cycle of flooding and draining that is repeated over time, similar to what a rain garden might experience in the landscape. Rain gardens are self-sustaining environments that only receive irrigation during a rain event and, as a result, may remain dry for a period of weeks until the next rain event regardless of soil type. Native plants adapted to low wetland areas are desirable for rain gardens because they are low maintenance, not invasive, relatively pest free (North Carolina Cooperative Extension, 2009), and usually able to persist during periods of low rainfall or drought once established (Dunnett and Clayden, 2007).
There has been little research evaluating specific plants for use in rain gardens. A variety of plant recommendation lists are available, but they are not based on data from replicated experiments [Cabrera, 2005; Ranney et al., 1998; U.S. Department of Agriculture (USDA), 2008; U.S. Fish and Wildlife Service, 1996 (USFWS)]. Such lists include, but are not limited to: “Qualifiers for quagmires: Landscape plants for wet sites” (Ranney et al., 1998); wetlands vascular plant species list (USFWS, 1996); “Plants for rain gardens” (Glen, 2009); “Wetland indicator status list” (USDA, 2008); “Shrubs for bioretention areas” (North Carolina Division of Water Quality, 2009); and lists of plants recommended for southern rain gardens (Kraus and Spafford, 2009). These lists were referred to to select plants used in this experiment. Since rain gardens may remain flooded for 2 d or longer depending on soil infiltration rate, plants should be able to survive and grow under periods of anaerobic conditions. The objective of this study is to determine the effects of short interval cyclic flooding on selected native shrubs intended for use in rain gardens, using substrates to simulate conditions in a standard and wet rain garden.
Cabrera, R.I. 2005 Challenges and advances in water and nutrient management in nursery and greenhouse crops Agricoltura Mediterranea 135 147 160
Dietz, M.E. & Clausen, J.C. 2008 Stormwater runoff and export changed with development in a traditional and low impact subdivision J. Environ. Manage. 87 560 566
Dunnett, N. & Clayden, A. 2007 Rain gardens: Managing water sustainability in the garden and designed landscape Timber Press Portland, OR
Dussaillant, A.R., Cuevas, A. & Potter, K.W. 2005 Stormwater infiltration and focused groundwater recharge in a rain garden: Simulations for different world climates. Sustainable Water Mgt Solutions Large Cities 293 178 184
Glen, C.D. 2009 Plants for rain gardens 7 Dec. 2009. <http://www.nhcgov.com/AgnAndDpt/COOP/Documents/Plants%20for%20Rain%20Gardens.pdf>.
Larson, K.D., Schaffer, B. & Davies, F.S. 1993 Physiological, morphological, and growth responses of mango trees to flooding Acta Hort. 341 152 159
Maryland Department of Environmental Resources 2007 The bioretention manual 30 June 2011. <http://www.princegeorgescountymd.gov/Government/AgencyIndex/DER/ESG/Bioretention/pdf/Bioretention%20Manual_2009%20Version.pdf>.
North Carolina Cooperative Extension 2009 Stormwater and your rain garden 7 Dec. 2009. <http://www.Bae.ncsu.edu/topic/raingarden/Entire_handout.doc>.
North Carolina Division of Water Quality 2009 Stormwater best management practices design manual 30 June 2011. <http://portal.ncdenr.org/web/wq/ws/su/bmp-ch12>.
Ranney, T.G., Bir, R.E., Powell, M.A. & Bilderback, T. 1998 Qualifiers for quagmires: Landscape plants for wet sites 10 Dec. 2008. <http://www.ces.ncsu.edu/depts/hort/hil/hil-646.html>.
Seo, S., Seggara, E., Mitchell, P.D. & Leatham, D.J. 2008 Irrigation technology adoption and its implication for water conservation in the Texas High Plains: A real options approach Agr. Econ. 38 47 55
Shuster, W.D., Gehring, R. & Gerken, J. 2007 Prospects for enhanced groundwater recharge via infiltration of urban storm water runoff: A case study J. Soil Water Conserv. 62 129 137
Stevens, R.M. & Prior, L.D. 1994 The effect of transient waterlogging on the growth, leaf gas exchange, and mineral composition of potted sultana grapevines Amer. J. Enol. Viticult. 45 285 290
U.S. Environmental Protection Agency 1983 Results of the nationwide urban runoff program U.S. Environ. Protection Agency Washington, DC
U.S. Fish and Wildlife Serv 1996 National list of vascular plant species that occur in wetlands: 1996 National summary 10 Dec. 2008. <http://wetlands.fws.gov/bha/download/1996/national.pdf>.
Wilkin, M.F. 2007 The effect of irrigation frequency on growth and physiology of native landscape shrub species Auburn Univ Auburn, AL M.S. Thesis
Wright, A.N., Warren, S.L., Blazich, F.A. & Blum, U. 2004 Root and shoot growth periodicity of Kalmia latifolia ‘Sarah’ and Ilex crenata ‘Compacta’ HortScience 39 243 247