5. Summary
These experiments establish that off-season greenhouse production of the SD strawberry cultivar ‘Sweet Charlie’ can be enhanced by conditioning plugs before planting in the greenhouse. The most effective conditioning treatment is seven 9 h short days at 21/21 °C (day/night) followed by seven 9 h short days at 21/12oC (day/night). A systematic evaluation of photoperiods, number of cycles and the timing and duration of chilling can help determine a conditioning protocol for off-season/winter strawberry production in North America. More efficient system development could be achieved by limiting the number of cultivars examined and focusing on those that produce high quality fruit. Photoperiod and temperature conditioning could be combined with other conditioning methods (propagation timing, fertilization and timing during conditioning, plug densities during propagation) to optimize off-season production. This study supports the hypothesis that chilling is effective in modifying floral initiation responses to photoperiod and demonstrates that the timing of the chilling treatment is critical for enhanced production responses. Yield enhancement due to conditioning treatment may not be realized as greater early yield, but rather may be expressed several months into the production cycle.