We assessed runner production in everbearing strawberry cultivars (Fragaria × ananassa Duch.) 'Natsuakari' and 'Dekoruju', which exhibit poor ability to produce runners, thus limiting their propagation and use. Both cultivars required 1,000 h of chilling (< 5°C) to induce runner production when grown under a long day length (LD); however, they required longer chilling under a short day length (SD). Plants chilled for 2,000 h tended to produce more runners under SD than under LD. During spring and summer, the overwintered 'Natsuakari' plants produced the fewest runners under SD. In contrast, the overwintered 'Dekoruju' plants produced the fewest runners under LD. Thus, a longer day length did not always enhance runner production in these cultivars. In autumn, 90-day cold storage at -2°C was substituted for natural chilling for plants that were rooted in summer. For both cultivars, the production of runners by plants that were rooted in July was similar to or greater than that by plants that were rooted in May. The rooting of mother plants in July, which are more available than plants rooted in May, did not have a detrimental effect on runner production during the next early summer period. Considering total runner production till July, we concluded that it is appropriate to initiate cold storage in December for the 'Natsuakari' cultivar and in November or December for the 'Dekoruju' cultivar.

Long-day treatments were applied to everbearing strawberry (Fragaria × ananassa Duch.) 'Natsuakari' before planting to accelerate flower initiation for the autumn harvest. Twenty-four-hour day length treatment for one month promoted the flower initiation of runner plants potted on May 30, June 17, July 1, and in the previous July. The yields of the first-year runner plants that were subjected to 24-h treatment were not lower than those of the plants potted in the previous July. An increase in day length led to a corresponding increase in flower initiation. Two weeks of treatment was sufficient for flower initiation in all the plants that underwent 24-h day length treatment or 4-h night interruption treatment. In the case of plants that underwent 16-h day length treatment, anthesis was observed in all of these plants after treatment for a total of one month. Three different planting dates after 24-h continuous or cyclic lighting (15 min・h −1 , overnight) treatments were investigated. As a result of 24-h continuous lighting for 3 weeks, harvesting could be initiated from early September for plants that were planted on July 28, but the yield in October was higher for the plants that were planted on August 10. Not all of the plants that were planted on September 2 could be harvested by December. Cyclic lighting was markedly less effective for flowering than continuous lighting.