Grape Phenology and GDD accumulation September 23, 2024 by Jennifer Morganthaler Grape Phenology and GDD accumulation GDD base 50 = 3377 . We track GDD at http://agebb.missouri.edu/weather/reports/gddTable.asp and rate the phenology stages according to the Modified E-L System https://door.extension.wisc.edu/files/2010/10/ModifiedEichhornLorennzsystem.pdf photos to follow…