Summary Single-node cuttings of sweet potato [(Ipomoea batatas (L.) Lam. ‘Beniazuma’)] were cultured in vitro for 35 d under intermittent blue light (IB), intermittent red light (IR) and intermittent blue-plus-red light (IBR) provided by light-emitting diodes (LEDs) flashing for 10 s three-times min–1. Growth was compared with cuttings cultured under continuous blue (B), red (R) or blue-plus-red (BR) light, or cool-white fluorescent lamps (FL) with a 16 h photoperiod. Dry weights, leaf areas and carbohydrate contents were greater under the IB and IBR treatments than in the FL treatment. Our results show that a novel light source during in vitro culture of sweet potato plantlets may provide an opportunity to improve plant yield in large-scale greenhouses for commercial purposes.