High-temperature effects on seed germination of fourteen Kentucky bluegrass (Poa pratensis L.) cultivars
¹Council for Agricultural Research and Economics, Via Ca' Nova Zampieri 37, IT 37057 S.G. Lupatoto (VR), Italy
²Council for Agricultural Research and Economics, Via Emilia km 307 19, IT 26838 Tavazzano (Lodi), Italy
³Department of Agronomy, Food, Natural resources, Animals and Environment, Padova University, Viale dell’Università 16, IT 35020 Legnaro (PD), Italy
Kentucky bluegrass (Poa pratensis L.) is a perennial cool-season grass commonly used for sport and ornamental turfgrasses in transition zones. It is a rather difficult species to establish due to slow germination and the relatively moderate growth rate of seedlings. Early autumn is considered the best time for sowing Kentucky bluegrass in temperate regions. Spring sowing is not recommended as low soil moisture and high temperatures can have a negative impact on germination. However, unavoidable circumstances often force turfgrasses to be sown in spring with high probability of failure. The risk of failure may increase in the near future as a consequence of climate change, so more knowledge is required on the ability of Kentucky bluegrass cultivars to germinate at high temperatures. A laboratory study evaluated the germination response of fourteen cultivars selected among those most used in northern Italy. They were compared in a conditioning chamber under five regimes of alternating temperatures (20/30 °C, 23/33 °C, 26/36 °C, 29/39 °C, 32/42 °C). Germination was recorded weekly starting from sowing. The germination patterns were similar up to 26/36 °C. At 29/39 °C only five cultivars had a germination of over 50%. At the highest temperature regime none of the cultivars had more than 3% germination. It is concluded that only when very extreme high temperatures occur, growers need to pay attention to the choice of cultivars to avoid problems during the germination-emergence phase, but based on the climate change scenario this is likely to happen with greater frequency in the future.