GDD base 50 = 1740. We track GDD at http://agebb.missouri.edu/weather/reports/gddTable.asp and rate the phenology stages according to the Modified E-L System http://door.uwex.edu/files/2010/10/ModifiedEichhornLorennzsystem.pdf The stage for the majority of grapes is 33 – Berries still hard and green. Mars is undergoing veraison. … [Read more...] about Grape phenology and GDD accumulation