Effects of Transplanting Date and Photoperiod on Flowering of Everbearing Strawberries

Everbearing strawberries have the potential to produce fruit year-round if transplanted early. However, temperature and plant physiological status limit the continuous flowering. Herein, we aimed to investigate whether promoting flowering through long-day phototreatment enables earlier transplanting. The interaction between transplanting date and photoperiod in two everbearing strawberry cultivars was examined. In the 04 cultivar, which exhibited strong everbearing characteristics, rapid and continuous flowering occurred largely independent of long-day treatment, and early transplanting alone increased inflorescence number and early yield. However, excessive flowering was associated with reduced average fruit weight, soluble solid concentration, and firmness. Conversely, in Yotsuboshi, a cultivar with weak everbearing characteristics, earlier transplanting combined with extended photoperiods advanced the emergence of the first and second inflorescences. However, gains in total early yield were small, and the average fruit weight decreased compared with that in the control, indicating physiological stress. Across the cultivars, earlier inflorescence emergence was negatively correlated with days to flowering and positively associated with cumulative yield. For practical applications, cultivars with strong everbearing characteristics can be managed with early transplanting and minimal long-day supplementation to ensure early production. In contrast, cultivars with weak everbearing characteristics require extended photoperiods following early transplanting along with stress-mitigation strategies to maintain fruit size and quality.