When to stop accumulating GDD's

[bhoenisch]

Most growing degree day references for grapes seem to use April though September or October as a standard. Here in Great Falls, MT we had our first frost/hard freeze on September 13th with a minimum temperature of 27F. My vines range from this years propagated and planted cuttings to mostly 2nd year vines and a single 3rd year Valiant. All are various cold Hardy hybrids. Many but not all leaves were fried by the cold. I really did not have much of a crop but was wondering if this is where I should stop accumulating growing degree days and call it a season or if any additional heat units would have any effect (if I did have a crop). I'm mostly wondering so that I can keep good records for reference I future years.

 

[GreginND]

Once the leaves are toast, there is no more energy going to ripening. Any grapes should be harvested asap.