It is the first of April when we begin recording GGD base 50 and track grapevine development. GDD base 50 accumulation for today = 0 http://agebb.missouri.edu/weather/reports/gddTable.asp  Phenology stages according to the Modified E-L System http://door.uwex.edu/files/2010/10/ModifiedEichhornLorennzsystem.pdf … [Read more...] about Grape phenology and GDD accumulation