GDD base 50 = 2102. 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 Chambourcin beginning to show some color. … [Read more...] about Grape phenology and GDD accumulation