Focus on Floriculture Vol 1 #1
The 9 to 11 month production schedule for potted hydrangeas is costly and includes development of a plant from a cutting, cold treatment, and forcing (2). We have worked with the effect of daylength on the life cycle of the crop and believe it is possible to produce hydrangea plants in 4 to 6 months, cutting to flowering plant, by eliminating pinching, long inflorescence initiation periods, leaf-drop treatment, and cold storage. Previous studies (4, 5, 8) and our present work indicate long daylengths delay the formation of the inflorescence, and in a 24 hour daylength (8 hours sunlight plus 20 ft. c. lighting for 16 hours) we found that plants continue to grow and do not display the vegetative and inflorescence dormancy previously thought to be characteristic of the crop and broken by cold treatment (3, 4, 7, 8, 9) or gibberellic acid (9). In 8 to 12 hour daylengths the plants were dormant. For example, 'Merveille1, with a inflorescence bud present but never given a leaf drop or cold treatment, flowered in about 50 days in a 70 F green house under a 24 hour daylength.
Keywords: Daylength inflorescence formation forcing characteristics Production scheme gibberellic acid