Growth Potential – An update on Growth-Degree-Days in that the Growth Potential (GP) model developed by Micah Woods uses an optimum temperature above which the GP declines. This is intended to take into account that there is a ceiling temperature for growth above which the plant experiences stress and the growth rate declines. Currently the GP model uses 20°C as this temperature, but experience from July 2014 leads me to the conclusion that the G.P model should be bsed on a lower temperature – 18°C.