BACKGROUND: As consumption of unripe mandarin increases, its cultivation has increased in open field cultivation areas. Because unripe mandarin must be harvested before ripening and color change, the optimum harvest time must be determined. This study investigated the effect of the harvest season on the yield of unripe fruit and biennial flowering of ‘Miyagawa’ satsuma mandarin.
METHODS AND RESULTS: Two areas of unripe mandarin orchard were selected, and the yield, fruit growth, working time, and flowering of trees the following year were investigated. Fruit was harvested at 40, 60, 80, 100, and 120 days after full bloom and at general ripening. Fruit yield of unripe mandarin increased with later harvest time from 100th to 120th day except normal ripening. The next year, biennial occurred with normal ripening and harvesting, but not at the 120th day after full bloom. At the 40th day (earliest harvest time), summer and autumn shoots were present, but not after the 100th day. The 40th day required the most harvesting time; because the time gradually decreased with later harvest, the harvest time was shortest on the 120th day, and general ripening occurred shortly after the 120th day .
CONCLUSION: Harvesting of unripe mandarin 100–120 days after full bloom was ideal to reduce harvesting time, enhance yield, and enable flowering the following year.