For Broccoli, the timing of growth stage progressions through the season is dependent on both the variety and environmental cues such as day length, or temperature. The Broccoli growing degree day model developed as part of the CROPTIME project at Oregon State University, uses heat units and time as a method to estimate plant phenological stages through the growing season. This can be helpful as a crop management tool, or to predict harvest timing.
Calculating Growing Degree Days
For this model, a lower temperature threshold of 32F and an upper threshold of 70F is used to calculate growing degree day accumulation beginning at the time of planting. Growing degree days can be calculated from daily high and low temperatures, using a sine model, or via the Pest Prophet app, which uses hourly temperature data for a given field. This can be used to predict head initiation, harvest, and flowering time for the following varieties: Arcadia, Emerald Pride, Green Magic or Imperial, based on growing degree day accumulation.
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