A software tool for scheduling production of cut flower stems of Rosa hybrida based on thermal units

In commercial cut-flower rose production harvests are scheduled by initiating bud breaks through pinching, pruning or bending of stems. Air temperature controls the rate of development of the flower stems so that a thermal unit (degree day) model can be used to describe the rate of development. The objective of this project was to develop and calibrate a software tool based on thermal units for use in scheduling rose production and for providing decision support with regard to greenhouse air temperature. Earlier work resulted in a model that has as its parameters the base temperature and the thermal-unit durations between various specific developmental events. The current project focused on the development of computer software to allow growers to use this model to manage rose crops, especially with regard to modern greenhouse practices (lighting, bending of stems). Our software forecasts dates of future developmental events in relation to past and anticipated temperature trajectories. As a result growers can determine whether temperatures need to be adjusted so as to achieve target harvest dates. The software tool also enables users to calibrate thermal unit parameters for any cut-flower rose variety. As part of the validation, flower production was tracked across nine growth cycles under various growth conditions and methods of flush initiation.