GDD base 50 = 93. 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 After three nights with temperature in the 20s, April 20 to 22, there was damage on the grapes. It was difficult to estimate today, but we think that … [Read more...] about Grape phenology and GDD accumulation