Wednesday, November 15, 2006

Cold Hardiness of Southern and Northern Saltgrass Ecotypes.

Mohamed A. Shahba, Sarah Wilhelm, Yaling Qian, and Anthony Koski. Colorado State University, Department of Horticultur and Landscape Arcitecture, Fort Collins, CO 80523-1173

Studies were conducted to assess cold hardiness of saltgrass accessions collected from southern climates (San Joaquin Valley, CA) vs. accessions collected from northern climate (the Front Range of Colorado). Plugs of three northern selections and three southern selections were planted in the field in Colorado to establish 5 by 5 ft plots. Rhizomes were sampled from the plots during November and December from 2003 to 2005 and subjected to laboratory freezing tests to determine freezing temperature resulting in 50% mortality (LT50). Field color evaluation indicated the northern accessions started dormancy response about one month earlier than the southern ecotypes. Significant differences existed between northern and southern ecotypes and within ecotypes. On average, the northern saltgrass ecotypes survived 7.0 to 13.0 C colder temperature than the southern ecotypes, with LT50 reaching 18 to 23 C during the mid-winter (January). Field winter injury was only observed during the winter of 2003-2004 when the southern accessions suffered 85-92% winter injury in the field whereas the northern accessions exhibited ≤ 10 % winter injury. No difference in field winter injury among ecotypes was observed in the winter of 2004-2005. In summary, southern ecotypes are less freeze tolerant than the northern ecotypes. This information is important in selecting and developing turf-type saltgrass accessions for regional use.