Manipulation of Cropping Time by Controlling Timing of Cane Elongation in Primocane-Fruiting Red Raspberry 'Heritage' in Japan

In Japan, raspberry (Rubus idaeus L.) imports have increased over the last decade and thus, the demand for domestic production. However, raspberry cultivation systems have not yet been established. A gap exists between cropping of floricane-fruiting and primocane-fruiting cultivars grown in open fields. To fill this gap and to extend the cropping period, we examined the effect of time of cane sprouting on cropping time using the primocane-fruiting red raspberry 'Heritage' grown in pots in Akita, northeast Japan. Control plants were grown in an open field until flowering. Canes were forced to sprout and grown in a plastic greenhouse. Delaying cane sprouting was examined by growing a second primocane 4 or 8 weeks after the first started to sprout. The primocane in the greenhouse sprouted 25 days earlier than the control plants. Canes delayed by 8 weeks did not blossom. The first day of cropping was 26 days earlier in the forced primocanes, and 31 days later in the canes which were delayed by 4 weeks, when compared with the control plants. No significant differences were observed between the treatments concerning yield, the period from primocane sprouting to flowering, and cropping periods. Therefore, early sprouting of raspberry canes by forcing in greenhouse could allow us to fill the gap between cropping periods. Delaying cane elongation by 4 weeks extended the period of cropping compared with the control plants. These results suggest a method for long-term stable cropping in northeastern Japan from the beginning of August to the middle of November using 'Heritage'.