Kentucky bluegrass (Poa pratensis L.) has been attempted to be grown in the transition zone; however, growing and maintaining this species throughout the year in this area can be difficult (Teuton et al., 2007). High humidity and high temperatures associated with summer and droughty soil conditions are often too stressful for kentucky bluegrass to thrive (Shearman, 1999). Diseases such as rust (Puccinia graminis Persoon subsp. graminicola Urban) and dollar spot (Sclerotinia homoeocarpa Bennett) can cause injury and a reduced stand in kentucky bluegrass (Landshchoot and Park, 1997; Wang and Huang, 2004).
Recently, the Scotts Company (Maryville, OH) released ‘Thermal Blue’ and ‘Dura Blue’ kentucky bluegrasses. These hybrid bluegrasses (P. arachnifera Torr. × P. pratensis L.) are interspecific hybrids of texas bluegrass (P. arachnifera Torr.) and traditional kentucky bluegrass. These hybrid bluegrass cultivars were bred for having the heat and drought tolerance of texas bluegrass and the desirable turfgrass quality of kentucky bluegrass (Abraham et al., 2004). Previous research has shown these turf cultivars have potential for use in the transition zone (Su et al., 2008; Teuton et al., 2007) and that these hybrids may impart more heat tolerance than actual drought tolerance (Abraham et al., 2008; Su et al., 2007).
Kentucky bluegrass is widely used in the transition zone and in the colder northern climates where optimum seeding rates, nitrogen fertility, and mowing heights are used (Beard, 1973; Bredakis, 1959; Jagschitz and Skogley, 1965; Juska and Hanson, 1961; Juska et al., 1955; Kuhn and Kemp, 1939; Skogley and Ledeboer, 1968). In general, kentucky bluegrass should be seeded between 50 to 100 kg·ha−1, which produces three to eight seed per square centimeter (Beard, 1973). However, many of the turfgrass breeders and developers have had problems with low seed yield, low germination rates, and poor seedling vigor in many of the new hybrid cultivars (Jim Frelich, personal communication). A literature search revealed minimal published information on seed establishment and maintenance of the hybrid bluegrasses. The objectives of these experiments were to: 1) determine optimal seeding rates; 2) establish the correct seed timing; and 3) investigate the interaction of mowing height and fertility requirements for ‘Thermal Blue’ and ‘Dura Blue’. These objectives are all specifically oriented toward the transition zone as previously described.
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