In the experiments reported here, "Annemarie" plants with at least three open flowers were transferred to growth rooms at 20 degsC. In one experiment, the rooms were lit for 12 hours a day. For one set of plants, the lighting was at low intensity every day but another set received low-intensity light for two days and high-intensity light every third day. Flower buds were removed to leave 20, 50 or 80 buds on each plant.
The high-intensity light treatment extended display life to more than 18 days and the largest number of open flowers under these conditions was found on plants that had 80 flower buds. By contrast, in the "low-light" treatment, the longest display life and the most open flowers were on plants with only 20 flower buds.
This suggests that growers could lengthen the display life of potted carnations marketed in winter by limiting the number of buds each plant carries and encouraging customers to move their plants to high-light areas whenever possible.
Effects of Light Intensity, Number of Florets, and Water Stress on Quality and Soluble Carbohydrate Contents of Potted Carnation by Yamane, Inotsume, Nakajima, Wada, Yamaki and Shimizu (2010). Journal of the Japanese Society for Horticultural Science 79 (3): 301-307. The authors' abstract is available online at www.jstage.jst.go.jp/browse/jjshs1 from where the article can be downloaded as a PDF.