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.
Alvarez, E.E. 2006 Salt and drought tolerance of four ornamental grasses. University of Florida, Gainesville, FL, MS thesis
Carter, C.T. & Grieve, C.M. 2006 Salt 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
Christova-Boal, D., Eden, R. & McFarlane, S. 1996 An investigation into greywater reuse for urban residential properties Desalination 106 391 397
Gavlak, R.G., Horneck, D.A. & Miller, R.O. 1994 Plant, soil, and water reference methods for the western region. Western Regional Ext. Publ. (WREP) 125
Grieve, C.M., Grattan, S.R. & Maas, E.V. 2012 Plant 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
Grieve, C.M., Poss, J.A., Grattan, S.R., Suarez, D.L., Benes, S.E. & Robinson, P.H. 2004 Evaluation of salt-tolerant forages for sequential water reuse systems II. Plant–ion relations Agr. Water Mgt. 70 121 135
Gunnell, J., Goodspeed, J. & Anderson, R.M. 2015 Ornamental 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/>
Kim, J., Liu, Y., Zhang, X., Zhao, B. & Childs, K. 2016 Analysis of salt-induced physiological and proline changes in 46 switchgrass (Panicum virgatum) lines indicates multiple response modes Plant Physiol. Biochem. 105 203 212
Kratsch, H., Olsen, S., Rupp, L., Cardon, G. & Heflebower, R. 2008 Soil salinity and ornamental plant selection. Utah State Univ. Coop. Ext., Logan, UT. 18 Dec. 2018. <https://digitalcommons.usu.edu>.
LeCompte, J.S., Wright, A.N., LeBleu, C.M. & Kessler, J.R. 2016 Saline irrigation affects growth and leaf tissue nutrient concentration of three native landscape plant species HortTechnology 26 309 313
Liu, Q., Sun, Y., Niu, G., Altland, J., Chen, L. & Jiang, L. 2017 Morphological and physiological responses of ten ornamental taxa to saline water irrigation HortScience 52 1816 1822
McKenney, C.B., Mahato, T.R. & Schuch, U.K. 2016 Salinity tolerance of ornamental grasses adapted to semi-arid environments Acta Hort. 1112 95 100
Missouri Botanical Garden 2018 Eragrostis spectabilis, Miscanthus sinensis ‘Gracillimus’, Panicum virgatum ‘Northwind’, and Schizachyrium scoparium. St. Louis, MO. 18 Dec. 2018. <www.missouribotanicalgarden.org/PlantFinder>
Netondo, G.W., Onyango, J.C. & Beck, E. 2004 Sorghum and salinity: II. Gas exchange and chlorophyll fluorescence of sorghum under salt stress Crop Sci. 44 806 811
Niu, G. & Cabrera, R.I. 2010 Growth and physiological responses of landscape plants to saline water irrigation: A review HortScience 45 1605 1609
Niu, G., Cabrera, R., Starman, T. & Hall, C. 2011 Water conservation in ornamental plant production through the use of alternative water sources HortTechnology 21 694 695
Scheiber, S.M., Sandrock, D., Alvarez, E. & Brennan, M.M. 2008 Effect of salt spray concentration on growth and appearance of ‘Gracillimus’ maiden grass and ‘Hameln’ fountain grass HortTechnology 18 34 38
Schiavon, M., Leinauer, B., Serena, M., Maier, B. & Sallenave, R. 2014 Plant growth regulator and soil surfactants’ effects on saline and deficit irrigated warm-season grasses: I. Turf quality and soil moisture Crop Sci. 54 2815 2826
Schiavon, M., Leinauer, B., Serena, M., Sallenave, R. & Maier, B. 2012 Bermudagrass and seashore paspalum establishment from seed using differing irrigation methods and water qualities Agron. J. 104 706 714
Sun, Q., Yamada, T. & Takano, T. 2015b Salinity effect on germination, growth, and photosynthesis, and ion accumulation in wild Miscanthus sinensis Anderss Populations. Crop Sci. 54 2760 2771
Taiz, L. & Zeiger, E. 2015 Plant physiology and development. 6th ed. Sinauer Associates, Sunderland, MA
Tanji, K., Grattan, S., Grieve, C., Harivandi, A., Rollins, L., Shaw, D., Sheikh, B. & Wu, L. 2008 A 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 Agriculture 2015 2014 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>
Wu, L. & Dodge, L. 2005 Landscape plant salt tolerance selection guide for recycled water irrigation. 18 Dec. 2018. <http://slosson.ucdavis.edu/Landscape_Plant_Selection_Guide_for_Recycled_Water_Irrigation/>
Wu, S., Sun, Y. & Niu, G. 2016 Morphological and physiological responses of nine ornamental species to saline irrigation water HortScience 51 285 290
Zhang, Q., Rue, K. & Wang, S. 2012 Salinity effect on seed germination and growth of two warm-season native grass species HortScience 47 527 530
Zhao, G.Q., Ma, B.L. & Ren, C.Z. 2007 Growth, gas exchange, chlorophyll fluorescence, and ion content of naked oat in response to salinity Crop Sci. 47 123 131