The first frost occurred yesterday, October 7 when it dropped to 30.4 degrees F at 7:05am. GDD base 50 accumulated since April 1 = +3919 (+472 departure from normal) at Mountain Grove http://agebb.missouri.edu/weather/reports/gddTable.asp March 2012 GDD base 50: 306+3919 = 4225 Phenology stages according to the Modified E-L system … [Read more...] about First frost and grapevine phenology and GDD accumulation