Climatic adaptability of annual bluegrass in Ohio using growing degree-days

Annual bluegrass (Poa annua L.) is a major turfgrass species in Ohio. Its reported poor heat tolerance makes it a difficult turfgrass species to maintain in areas where periods of high temperatures exist. The purpose of this study was to determine areas in Ohio based on growing degree-days where annual bluegrass is adapted. Thirty-year averages of minimum and maximum daily temperatures from 15 locations were used. A BASIC computer program was written to calculate and accumulate growing degree-days (GDD) and temperature stress degree-days (TSDD) using a sine curve as an approximation of the diurnal temperature curve. Based on TSDDs, annual bluegrass was best adapted to northern Ohio and least adapted to southern Ohio. In this study, TSDDS were useful in determining regions of annual bluegrass adaptation. Scientists involved in determining climatic regions of plant adaptation may want to consider using TSDDs as a method for quantifying temperature effects.