Off season induction of flowering and fruit production is a desirable economical and scientific goal with many subtropical fruit trees. Both objectives have been accomplished by the application of gibberellin biosynthesis inhibitors with mango and a few other fruit trees. Recently the same was achieved with longan trees (Dimocarpus longan, Lour.) after treatment with potassium chlorate. This treatment allows the efficient induction of flowering and fruit production all over the year in an obviously species-specific manner. Experiments are described that investigated several aspects of this KClO 3 treatments, such as methods of application, seasonal effects, reactiveness of different cvs. toward the chemical, influence of leaf age, etc. The results are discussed with respect to the practical application of KClO 3 for off season fruit production, but also under the aspect of its use for more basic investigations into the endogenous regulation of the flowering induction process in perennial fruit trees. © 2005 Elsevier B.V. All rights reserved.