Effects of light and temperature on growth and flowering of carnation (Dianthus caryophyllus L.)

Both a long photoperiod and strong illumination strongly promoted growth and flowering. These conditions diminished the number of leaf pairs below the flower and promoted growth of flower buds from initiation to bud emergence from the leaves. The subsequent phases to anthesis were little affected by photoperiod and light intensity. Other characters such as stem length, stem diameter, leaf length and width, flower diameter and petal number were affected more by strength than by duration of illumination.

Flower induction was promoted by cold (5°C). But as soon as the flower had been initiated, its development was promoted by warmth.

Carnations were planted the year round at two-week intervals. The shortest time between planting and harvest was 4 months, after planting in April, the longest 8 months, after planting in September. Treatment at 5°C for three weeks reduced the time to the first crop when plants were started between July and November and increased it in plantings between January and June. There was no residual effect of cold on the second crop.