More than 80% of the U.S. population lives in urban areas (U.S. Census Bureau, 2010). Residential and commercial districts may cover 20% and 85% of the land with impervious surfaces, respectively (Dietz and Clausen, 2005). Increasing the area covered by impervious surfaces decreases water infiltration and increases the amount of stormwater runoff [U.S. Environmental Protection Agency (U.S. EPA), 1993]. Urban runoff contains sediment, soil nutrients, road salts, petroleum hydrocarbons, and heavy metals (Dietz and Clausen, 2005; U.S. EPA, 2005), and the resulting pollution is responsible for 36,305 impaired river km, 283,689 impaired lake ha, and 2246 impaired estuary km2 in the United States (U.S. EPA, 2009). The quality of urban runoff can be improved and the quantity greatly reduced by using a rain garden.
A rain garden is a shallow depression in the landscape, typically planted with herbaceous perennials, shrubs, or small trees, that collects stormwater from impervious surfaces such as roofs, driveways, or parking lots (Dietz, 2007; Dietz and Clausen, 2006). Rain gardens allow stormwater to infiltrate into the ground and recharge groundwater supplies (Dietz and Clausen, 2006; Shuster et al., 2007) while removing stormwater pollutants (U.S. EPA, 1999). Ponded water in a rain garden should not remain longer than 24 h and the soil pore space should drain within 48–96 h (Davis et al., 2009; MPCA, 2015). During periods of frequent rainfall events or in situations where the rain garden does not drain as designed, ponded water may remain for several days.
Rain garden plants depend on seasonal precipitation and will be subjected to cyclical flooding and drought. The U.S. EPA (1999) recommends using native plants tolerant of pollutants and varying amounts of soil moisture. Sedges belong to the genus Carex and are commonly recommended for rain gardens (Bannerman and Considine, 2003; Shaw and Schmidt, 2003). Sedges are herbaceous perennials with ≈2000 species distributed worldwide and found in a wide range of habitats (Ball 1990; Bernard, 1990; Reznicek, 1990) such as wet meadows, pond and lake edges, dry grasslands, and mesic and dry forests (Schütz, 2000). It is estimated that 500 species occur in North America (Catling et al., 1990).
Few studies are available that evaluate the flood tolerance of sedges. Moog and Janiesch (1990) evaluated root growth of longbract sedge (Carex extensa Goodenough), remote sedge (Carex remota L.), and cypress-like sedge (Carex pseudocyperus L.) with soil moisture preferences of dry, moist, and saturated, respectively. Under flooded and anaerobic conditions, they found an increase in total biomass for remote sedge and cypress-like sedge, the two sedges that preferred moist and saturated soils, but not longbract sedge. A similar study by Visser et al. (2000) evaluated flood tolerance and aerenchyma formation of six alpine meadow sedges distributed in the meadow based on soil water content with evergreen sedge (Carex sempervirens Vill.) and rust-colored sedge (Carex ferruginea Scop.) growing in nonflooded soil, Davall’s sedge (Carex davalliana Sm.) and smooth black sedge [Carex nigra (L.) Reichard] in water-logged soil, and mud sedge (Carex limosa L.) and beaked sedge (Carex rostrate Stokes) partially submerged in water. Field-collected sedges were placed in flooded (water level at soil surface), submerged (water level 5 cm above soil surface), and drained (watered as needed) conditions for 150 d. Although evergreen sedge and rust-colored sedge grow in nonflooded soil, both tolerated flooded conditions for 150 d with similar shoot and root dry weights when compared with the drained treatment. The authors also evaluated aerenchyma formation of the sedges by growing them in stagnant or aerated nutrient solutions. Aerenchyma increased in all species grown in oxygen-deficient conditions compared with the aerated nutrient solution (Visser et al., 2000). Aerenchyma tissue improves internal root aeration (Kozlowski, 1997).
Luo et al. (2008) evaluated flooding and drought tolerance of three Chinese wetland plants: woollyfruit sedge (Carex lasiocarpa Ehrh.), mud sedge (C. limosa L.), and narrow-leaf small reed [Deyeuxia angustifolia (Komarov) Y.L. Chang], which typically occur in water depths of 10–50, 10–30, and 0–10 cm, respectively. Flooding tolerance was assessed over a 25-d period and water depth was maintained at 50 cm above the soil surface. At the end of the study, survival of woollyfruit sedge, mud sedge, and narrow-leaf small reed were 100%, 44%, and 11%, respectively. Drought tolerance of these three species was also assessed. Soil water content was measured daily over the 25-d study and decreased to 0.1% by the experiment’s end. The only plants surviving were narrow-leaf small reed, suggesting that plants surviving flooding may not be able to survive drought.
Sedge species such as gray’s sedge, palm sedge, pennsylvania sedge, plains oval sedge, porcupine sedge, sprengel’s sedge, and yellow fox sedge have been recommended for rain garden use (Bannerman and Considine, 2003; Hausken and Thompson, 2015; HHRCDC, 2017; Rodie et al., 2010; Schmidt et al., 2007; Shaw and Schmidt, 2003), but no scientific studies have been published to support these recommendations. Our objective was to determine the effect of cyclical flood and drought on the growth of these seven sedge species to determine their fitness for rain garden use.
BannermanR.ConsidineE.2003Rain gardens: A how-to manual for homeowners. Univ. Wisc. Ext. Coop. Publ. GWQ037
BlakeG.R.HartgeK.H.1986Particle density p. 377–382. In: A. Klute (ed.). Methods of soil analysis: Part 1–physical and mineralogical methods. SSSA ASA Madison WI
BrateriesK.FletcherT.D.DelecticA.ZingerY.2008Nutrient and sediment removal by stormwater biofilters: A large-scale design optimization studyWater Res.42143930–3940
CatlingP.M.ReznicekA.A.CrinsW.J.1990Introduction (special issue) systematics and ecology of the genus Carex (Cyperaceae)Can. J. Bot.6814051408
DettmannU.BechtoldM.2018Evaluating commercial moisture probes in reference solutions covering mineral to peat soil conditionsVadose Zone J.17170208
DietzM.E.2007Low impact development practices: A review of current research and recommendations for future directionsWater Air Soil Pollut.186351363
DylewskiK.L.WrightA.N.TiltK.M.LeBleuC.2011Effects of short interval cyclic flooding on growth and survival of three native shrubsHortTechnology21461465
FarooqM.HussainM.WahidA.SiddiqueK.H.M.2012Drought stress in plants: An overview p. 1–36. In: R. Aroca (ed.). Plant responses to drought stress from morphological to molecular features. Springer New York NY
HauskenS.ThompsonG.2015Rain garden plants. 21 Apr. 2015. <http://www.extension.umn.edu/garden/yard-garden/landscaping/best-plants-for-tough-sites/docs/08464-rain-garden.pdf>.
Hooiser Heartland Resource Conservation and Development Council (HHRCDC)2017Build your own rain garden: Plant selection and planting schemes. 1 May 2017. <http://hhrcd.org/pdf/Rain%20Garden-FS-plants-final.pdf>.
JerniganK.J.WrightA.N.2011Effect of repeated short interval flooding events on root and shoot growth of four landscape shrub taxaJ. Environ. Hort.29220222
KozlowskiT.T.1997Responses of woody plants to flooding and salinity. Tree Physiol. Monogr. No. 1 p. 1–29
Minnesota Pollution Control Agency (MPCA)2015Minnesota storm water manual. MPCA. 21 Apr. 2015. <http://stormwater.pca.state.mn.us/index.php/Main_Page>.
ReadJ.WevillT.FletcherT.DeleticA.2008Variation in plant species in pollutant removal from stormwater in biofiltration systemsWater Res.42893902
RodieS.HartsigT.SzatkoA.2010Sustainable landscapes: Rain gardens bioswales and xeric gardens: Managing rain water in your yard: A manual for homeowners and small properties. City of Omaha NE. 24 June 2017. <http://omahastormwater.org/download/227/manuals/id:5p9DrKDnFmAAAAAAAAACDQ/Sustainable%20Landscapes%20Manual>.
SchmidtR.SchawD.B.DoddsD.2007The blue thumb guide to rain gardens: Design and installation for homeowners in the upper midwest: A guide for planting zonse 3 4 and 5. Waterdrop Innovations River Falls WI
ShawD.SchmidtR.2003Plants for stormwater design: Species selection for the Upper Midwest. Minnesota Pollution Control Agency. 4 Oct. 2018. <http://www.pca.state.mn.us/water/plants-stormwater-design>.
ShusterW.D.GehringR.GerkenJ.2007Prospects for enhanced groundwater recharge via infiltration of urban storm water runoff : A case studyJ. Soil Water Conserv.62129137
SigmonL.HoopesS.BookerM.WatersC.SalpeterK.TouchetteB.2013Breaking dormancy during flood and drought: Sublethal growth and physiological responses of three emergent wetland herbs used in bioretention basinsWetlands Ecol. Mgt.214554
TinerR.W.2012Defining hydrophytes for wetland identification and delineation. ERDC/CRREL CR-12-1. U.S. Army Corps of Engineers Washington D.C
TurkR.P.KrausH.T.HuntW.F.CarmenN.B.BilderbackT.E.2017Nutrient sequestration by vegetation in bioretention cells receiving high nutrient loadsJ. Environ. Eng.143206016009
U.S. Census Bureau2010Census data 2010. U.S. Census Bureau. 10 Dec. 2014. <http://www.census.gov/2010census/data/>.
U.S. Department of Agriculture Natural Resource Conservation Service2015The plants database. National Plant Data Team Greensboro NC 27401-4901. 21 Apr. 2015. <http://plants.usda.gov>.
U.S. EPA1993Handbook of urban runoff pollution prevention and control planning. EPA-625-R-93/004. U.S. Environmental Protection Agency Cincinnati OH
U.S. EPA1999Storm water technology fact sheet: Bioretention. EPA-832-F-99-012. U.S. Environmental Protection Agency Washington D.C
U.S. EPA2005National management measures to control nonpoint source pollution from urban areas. EPA-841-B-05-004. U.S. Environmental Protection Agency Washington D.C. 20460
U.S. EPA2009National water quality inventory: Report to congress 2004 reporting cycle. EPA-841-R-08-001. U.S. Environmental Protection Agency Washington D.C. 20460
VisserE.T.W.BogemannG.M.Van de SteegH.M.PierikR.BlomC.W.P.M.2000Flood tolerance of Carex species in relation to field distribution and aerenchyma formationNew Phytol.14893103