Strawberry (Fragaria x ananassa Duch. cv. 'Hecker' and cv. 'Summerberry') plants were grown at 30/25 °C under an 8-hr photoperiod in phytotrons from June to September (for 16 weeks). As a result, flower bud initiation (FBI) was completely inhibited by the 16th week. Then, these plants were grown under 8- or 24-hr photoperiods at 20/15 °C or 30/25 °C. In these environments, except under the 8-hr photoperiod at 30/25 °C, the plants resumed FBI. These results indicate that the flowering response of these cultivars is qualitative under high temperature and quantitative under low temperature.