Water conservation is becoming critically important throughout the United States, especially in Utah and the Intermountain West, one of the driest and fastest growing regions in the United States. The green industry in this arid to semiarid region would earnestly consider alternative water sources such as treated and reclaimed sewage effluent (reclaimed water) for water conservation and improved environmental stewardship. Reclaimed water has been a viable alternative source for landscape irrigation in Utah, with an established use record on golf courses. Reclaimed water is also used by a handful of large corporate and municipal parks and landscapes in arid and semiarid urban areas across the Desert Southwest (Grieve, 2011; Tanji et al., 2008). As Utah and the West work toward improved water conservation, the chances are good that water will be restricted until only minimums are applied. This has the potential to reduce the leaching fraction of irrigation to the point that soil salinity will gradually increase, especially in salt-prone areas using reclaimed water. It is essential to select salt-tolerant plants for landscape use in those salt-prone areas.
Reclaimed water has a relatively high salinity level and undesirable specific ions (Grieve, 2011) that could impose salt stress on a large number of landscape plants (Niu and Cabrera, 2010; Sun et al., 2015a; Wu and Dodge, 2005). Landscape plants have been evaluated for salt tolerance. Since 2005, researchers at the Texas A&M AgriLife Research Center at El Paso have screened more than 150 landscape plant species and/or cultivars in greenhouse conditions (Niu and Cabrera, 2010; Niu et al., 2011; Sun et al., 2015a). All these studies showed consistently that the salt tolerance of landscape plants varies highly with species and/or cultivars (Chen et al., 2017; Liu et al., 2017; Sun et al., 2015a). However, limited research-based information on the salt tolerance of ornamental grasses is available.
Ornamental grasses have drawn considerable attention in the U.S. green industry as a result of their high drought tolerance, low maintenance input, and the unique textures and patterns they contribute to the landscape (Gunnell et al., 2015). Nursery production and landscape use have expanded significantly, with an estimated $158 million worth of ornamental grasses sold annually in the United States (U.S. Department of Agriculture, 2015). Ornamental grasses are popular in urban landscapes in Utah and the Intermountain West of the United States. Eragrostis spectabilis (purple love grass) is a warm-season bunchgrass with flat, coarse green leaves and soft reddish purple flowers in a loose and open inflorescence (Missouri Botanical Garden, 2018). The inflorescence of purple love grass is good for dried flower arrangements. Miscanthus sinensis ‘Gracillimus’, commonly called chinese silver grass or maiden grass, is a clump-forming warm-season grass that features narrow green leaves with a silver midrib and tiny reddish copper flowers in tassel-like inflorescences (Missouri Botanical Garden, 2018). Maiden grass produces long-lasting dried flowers for winter interest. Panicum virgatum ‘Northwind’ (switchgrass), an introduction of Northwind Perennial Farm (Burlington, WI), is a warm-season grass with finely textured, pink-tinged, branched panicle inflorescences and olive- to bluish green foliage forming a compact, narrow, erect clump (Missouri Botanical Garden, 2018). Schizachyrium scoparium (little bluestem) is one of the dominant grasses of the tallgrass prairie region and features upright clumps of slender, flat, linear green leaves with purplish bronze flowers in racemes (Missouri Botanical Garden, 2018). These four ornamental grass species belong to the grass family (Poaceae). They tolerate a wide range of soils and drought conditions and are accent specimens for garden and urban landscapes.
The salt tolerance of a few ornamental grasses have been evaluated. In general, cool-season grasses usually have less salt tolerance than warm-season grasses (Schiavon et al., 2012, 2014). In a 4-month experiment, Leymus arenarius (L.) Hochst. (sand ryegrass), Muhlenbergia capillaris (Lam.) Trin. (pink muhly grass), and Pennisetum alopecuroides (L.) Spreng. (fountain grass) showed a very strong salt tolerance with an acceptable visual quality, although plant growth was inhibited by the increasing salinity (Sun and Palmer, 2018). Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths (blue grama) has moderate tolerance to salinity when grown at a saturated soil extract (ECe) of 4 to 8 dS·m–1 (Kratsch et al., 2008), and its salt tolerance varies within ecotypes and is greater at the germination stage than the mature stage (Zhang et al., 2012). P. alopecuroides ‘Hameln’ is slightly more tolerant to salt spray than M. sinensis ‘Gracillimus’ (Alvarez, 2006). Pennisetum clandestinum Hochst. ex Chiov. (kikuyugrass) is a suitable candidate for the saline–sodic water reuse system with a threshold ECe of 8.0 dS·m–1 (Grieve et al., 2004, 2012). Pink muhly grass can survive at sodium chloride (NaCl) irrigation rates of 10,000 mg·L–1 (corresponding to an EC of ≈12.5 dS·m–1), which is up to 20 times greater than graywater (Christova-Boal et al., 1996; LeCompte et al., 2016). Because diverse ornamental grasses are produced by the green industry, further research is needed to identify salt-tolerant ornamental grasses for landscape use. This study was designed to assess the salt tolerance of four commonly used ornamental grasses in response to saline solution irrigation through comparing their growth, gas exchange, and mineral nutrients.
AlvarezE.E.2006Salt and drought tolerance of four ornamental grasses. University of Florida Gainesville FL MS thesis
CarterC.T.GrieveC.M.2006Salt tolerance of floriculture crops p. 279–287. In: M.A. Khan and D.J. Weber (eds.). Ecophysiology of high salinity tolerant plants. Springer Science + Business Media Dordrecht The Netherlands
GavlakR.G.HorneckD.A.MillerR.O.1994Plant soil and water reference methods for the western region. Western Regional Ext. Publ. (WREP) 125
GrieveC.M.GrattanS.R.MaasE.V.2012Plant salt tolerance p. 405–459. In: W.W. Wallender and K.K. Tanji (eds.). Agricultural salinity assessment and management. 2nd ed. ASCE Manual and Rpt. Eng. Practice No. 71. American Society of Civil Engineering Reston VA
GrieveC.M.PossJ.A.GrattanS.R.SuarezD.L.BenesS.E.RobinsonP.H.2004Evaluation of salt-tolerant forages for sequential water reuse systems II. Plant–ion relationsAgr. Water Mgt.70121135
GunnellJ.GoodspeedJ.AndersonR.M.2015Ornamental grasses in the landscape: A guide for the Intermountain West. Utah State Univ. Ext. Logan UT. 18 Dec. 2018. <https://digitalcommons.usu.edu/extension_curall/733/>
KimJ.LiuY.ZhangX.ZhaoB.ChildsK.2016Analysis of salt-induced physiological and proline changes in 46 switchgrass (Panicum virgatum) lines indicates multiple response modesPlant Physiol. Biochem.105203212
KratschH.OlsenS.RuppL.CardonG.HeflebowerR.2008Soil salinity and ornamental plant selection. Utah State Univ. Coop. Ext. Logan UT. 18 Dec. 2018. <https://digitalcommons.usu.edu>.
LeCompteJ.S.WrightA.N.LeBleuC.M.KesslerJ.R.2016Saline irrigation affects growth and leaf tissue nutrient concentration of three native landscape plant speciesHortTechnology26309313
LiuQ.SunY.NiuG.AltlandJ.ChenL.JiangL.2017Morphological and physiological responses of ten ornamental taxa to saline water irrigationHortScience5218161822
Missouri Botanical Garden2018Eragrostis spectabilis Miscanthus sinensis ‘Gracillimus’ Panicum virgatum ‘Northwind’ and Schizachyrium scoparium. St. Louis MO. 18 Dec. 2018. <www.missouribotanicalgarden.org/PlantFinder>
NetondoG.W.OnyangoJ.C.BeckE.2004Sorghum and salinity: II. Gas exchange and chlorophyll fluorescence of sorghum under salt stressCrop Sci.44806811
NiuG.CabreraR.StarmanT.HallC.2011Water conservation in ornamental plant production through the use of alternative water sourcesHortTechnology21694695
ScheiberS.M.SandrockD.AlvarezE.BrennanM.M.2008Effect of salt spray concentration on growth and appearance of ‘Gracillimus’ maiden grass and ‘Hameln’ fountain grassHortTechnology183438
SchiavonM.LeinauerB.SerenaM.MaierB.SallenaveR.2014Plant growth regulator and soil surfactants’ effects on saline and deficit irrigated warm-season grasses: I. Turf quality and soil moistureCrop Sci.5428152826
SchiavonM.LeinauerB.SerenaM.SallenaveR.MaierB.2012Bermudagrass and seashore paspalum establishment from seed using differing irrigation methods and water qualitiesAgron. J.104706714
SunQ.YamadaT.TakanoT.2015bSalinity effect on germination, growth, and photosynthesis, and ion accumulation in wild Miscanthus sinensis AnderssPopulations. Crop Sci.5427602771
TaizL.ZeigerE.2015Plant physiology and development. 6th ed. Sinauer Associates Sunderland MA
TanjiK.GrattanS.GrieveC.HarivandiA.RollinsL.ShawD.SheikhB.WuL.2008A comprehensive literature review on salt management guide for landscape irrigation with recycled water in coastal southern California. 18 Dec. 2018. <www.salinitymanagement.org>
U.S. Department of Agriculture20152014 Census of horticultural specialties Table 25. Washington DC. 18 Dec. 2018. <https://www.agcensus.usda.gov/Publications /2012/Online_Resources/Census_of_Horticulture_Specialties/hortic_1_004_004.pdf>
WuL.DodgeL.2005Landscape plant salt tolerance selection guide for recycled water irrigation. 18 Dec. 2018. <http://slosson.ucdavis.edu/Landscape_Plant_Selection_Guide_for_Recycled_Water_Irrigation/>
WuS.SunY.NiuG.2016Morphological and physiological responses of nine ornamental species to saline irrigation waterHortScience51285290
ZhaoG.Q.MaB.L.RenC.Z.2007Growth, gas exchange, chlorophyll fluorescence, and ion content of naked oat in response to salinityCrop Sci.47123131