AbstractThe effects of photoperiod, temperature and chilling on growth and flower formation in strawberry are briefly described, and the evidence for postulating a vegetative growth-promoting hormone is discussed. The hormone apparently inhibits flower formation. The similarity between the activities of the hormone and of exogenous gibberellins are reviewed and the tentative conclusion drawn that although increased biosynthesis of gibberellins is part of the photoperiodic response the natural hormone messenger between leaf and apex cannot be an active gibberellin like gibberellic acid, although it could be an inactive form or a precursor. There is evidence for a second independent photoperiodic factor operating on petiole growth. Photo-periodic stimuli and exogenous gibberellic acid are additive in their inhibition of flowering but this does nut necessarily mean that the two act in the same metabolic pathway. Abscisic acid promotes flowering and extracts of dormant strawberry leaves contain abscisic acid. Extracts of non-dormant leaves and of stolon tips are active in the lettuce hypocotyl test for gibberellins. CCC (Chlormequat chloride; (2-chloroethyl)-trimethylammonium chloride) depresses vegetative growth but does not usually promote flower formation.