For Roses, the timing of flowering shoot development is dependent on both the variety and environmental cues such as day length, or temperature. The Rose flowering shoot growing degree day model developed by researchers, 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 timing to harvest flowering shoots.

Calculating Growing Degree Days

For this model, a lower temperature threshold of 41.4F 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, or via the Pest Prophet app, which uses hourly temperature data for a given field. This can be used to predict leaf development, flower buds, and harvest, based on growing degree day accumulation, for the following varieties: Cara Mia, Royalty and Sonia.

Source:

Pasian, C.C., and J.H. Lieth. 1994. Prediction of flowering rose shoot development based on air temperature and thermal units. Scientia Horticulturae 59:131-145.

Pasian, C.C., and J.H. Lieth. 1996. Prediction of rose shoot development: model validation for the cultivar ‘Cara Mia’ and extension to the cultivars ‘Royalty’ and ‘Sonia’. Scientia Horticulturae 66:117-124.