In Northern Italy, two trials have been performed on Lilium and poinsettia cultivars to control plant height by day–night temperature regimes. Two identical glasshouse compartments have been used for the experiments: one maintained at standard conditions (the same minimum and ventilation temperatures during day and night), the other with minimum day temperature lower than night. Cultivations of lilies and poinsettias started in Winter and Summer 1993, respectively, with different climate conditions (cold in winter and hot in summer). Results on Lilium indicated that a good control of greenhouse temperature can be achieved in Italy's winter climate, even on sunny days; the best height reduction (30%) was obtained on Lilium longiflorum cv. `White American', compared to other Lilium species. Test on poinsettia have been based mainly on controlling ventilation of the glasshouse to raise temperature in the first part of the night and to lower it during the first daytime hours.
If the inline PDF is not rendering correctly, you can download the PDF file here.