The timing of the induction of flowering determines to a large extent the reproductive success of plants. Plants integrate diverse environmental and endogenous signals to ensure the timely transition from vegetative growth to flowering. Carbohydrates are thought to play a crucial role in the regulation of flowering, and trehalose-6-phosphate (T6P) has been suggested to function as a proxy for carbohydrate status in plants. The loss of TREHALOSE-6-PHOSPHATE SYNTHASE 1 (TPS1) causes Arabidopsis thaliana to flower extremely late, even under otherwise inductive environmental conditions. This suggests that TPS1 is required for the timely initiation of flowering. We show that the T6P pathway affects flowering both in the leaves and at the shoot meristem, and integrate TPS1 into the existing genetic framework of flowering-time control.