Use of LED lights in rooting and quality of landscape rose cuttings

Light has long been used in greenhouses to increase crop yields, to achieve offseason production, or to schedule production. The recent development of LED technology represents an opportunity for the development of horticultural production. One of the limitations for the wide diffusion of this technology is the species specificity of responses to light treatments, also depending on the goal being pursued. In this context this work wanted to investigate the effect of different light intensities and spectral composition when used as supplemental lighting, on the rooting of landscape rose cuttings in the summer season. Two different spectral compositions were compared: 100% red and 70% red with 30% blue, at 30 and 60 μmol m-2 s-1, in comparison with a control without supplemental lighting. Single-node cuttings of four cultivars were used: ‘Aspirin’, ‘Austriana’, ‘Centro’ and ‘Mirato’. Two rooting cycles were carried out. The results highlighted differences in the two rooting cycles, with better results being obtained in the first one. There were also obvious differences in the response of the cultivars, with ‘Austriana’ benefitting most from the supplemental lighting. With respect to light treatments, the control produced poor results, while the adoption of LED lighting improved both the yield and the quality, in particular when providing 60 μmol m-2 s-1 but with no differences being observed between the two spectral compositions tested.