Abstract
Newer light-emitting diode (LED) lighting technology increases the feasibility of inexpensively regulating strawberry ( Fragaria x ananassa Duch.) plant development during propagation to enhance fruit production. Nitrogen fertilization and short-term cold storage also influence flowering and fruit production. Two experiments were designed to develop specific treatment combinations to enhance off-season productivity of both long-day (LD) and short-day (SD) cultivars. In one experiment, plugs of ‘Albion’ were conditioned with far-red + red light as a night interruption, ± elevated nitrogen, ± short-term cold storage (chilling) followed by greenhouse forcing. Elevated nitrogen or a night interruption enhanced inflorescence production and, combined with short-term chilling, enhanced precocity. In a second experiment, plugs of ‘Chandler’, ‘Ruby June’, ‘Ashley Jay’, ‘Sensation’, ‘Miss Jo’ and the Lassen Canyon Nursery selection ‘122 × 08’ were exposed to far-red and red light during the nyctoperiod, followed by short-term cold storage, flower mapping and greenhouse forcing. Initiation in ‘Chandler’ was inhibited by far-red + red as a night interruption. In ‘Miss Jo’, red at the end of the nyctoperiod enhanced initiation, and in ‘122 × 08’, far-red at the end of the nyctoperiod enhanced initiation. Similar effects on differentiation were observed. In ‘122 × 08’, red at the end of the nyctoperiod enhanced inflorescence production (development), and in ‘Ashley Jay’, chilling enhanced development, albeit by a very small amount. In ‘Ruby June’, chilling enhanced development, but only for the far-red + red night interruption treatment. Short-term chilling of ‘Albion’ plugs prior to planting is not recommended for conditioned plants since chilling may delay flowering by 2.5 weeks. Conditioning of SD cultivars is minimally effective and thus not recommended.