In multi-layer cultivation of tulip flowers, up to 50% of energy saving can be achieved compared to a single layer crop. Even more energy can be saved if the evaporation can be reduced. However, the risk of physiological abnormalities like ‘tipping’ increases with reduced evaporation. In the framework of the Long-Term Agreement on Energy in Flowerbulbs, Wageningen University & Research Flower Bulbs demonstrated in 2017 that the sensitivity to tipping is limited to a few days during the cultivation, and only for a number of hours per day. The duration and exact phase of sensitivity to tipping are cultivar dependent, and Calcium fertilization also plays a role. If tulips are grown in this sensitive phase at low RH (about 70%) and in the remaining period at RHs to 100%, up to an extra 47% could be saved on energy. This insight is useful not only for multi-layer cultivation, but also for single-layer cultivation.