Typically, in forcing culture of strawberry (Fragaria × ananassa Duch.), plants raised in a nursery are transplanted to fields immediately after low temperature and dark treatments for the induction of terminal inflorescence. However, often after transplantation, the flowering of the primary axillary inflorescence is delayed due to a high field temperature after transplanting. Here, we analyzed a method for reducing the flowering delay. We noted that the flowering delay could be reduced by maintaining the plants in the nursery for an extended period of three weeks and applying 2 g of isobutylidenediurea fertilizer containing 10% nitrogen to each plant maintained under 50% shade. Our results showed the reduction of flowering delay in non-transplanted plants compared with transplanted ones. This treatment was found to be useful in reducing flowering delay of the primary axillary inflorescence regardless of the climatic conditions after transplanting, and, therefore, could contribute to obtaining stable yields in the forcing culture of the strawberry cultivar ‘Fukuoka S6’.