Effects of Chilling Duration on Time to Shoot Emergence and Subsequent Growth of Hosta

Abstract

Abstract Eight hosta species or cultivars, Hosta plantaginea, H. ventricosa ‘Aureo Marginata’, H. ‘Tokudama’, H. ‘Francee’, H. ‘Sum and Substance’, H. ‘Fragrant Bouquet’, H. ‘Frances Williams’, and H. sieboldiana ‘Elegans’, were chilled in a walk-in cooler in two-week increments from 2 to 10 weeks at 4C (39F), prior to forcing in a heated greenhouse. More than 80% of all cultivars in all treatments emerged, except for H. ‘Tokudama’. For all cultivars tested, days to shoot emergence and days to first leaf unfurled decreased quadratically as chilling duration increased. Most rapid decreases occurred between 0 and 6 weeks of chilling. In the absence of chilling, H. plantaginea was the first cultivar to emerge, between 34 and 79 days before other cultivars. H. plantaginea was followed by H. ventricosa ‘Aureo Marginata’, H. ‘Sum and Substance’, and H. ‘Fragrant Bouquet’, all of which emerged before H. ‘Frances Williams’. Leaf area index, an indicator of plant vigor, increased linearly as chilling duration increased. Shoot dry weight increased in H. ‘Fragrant Bouquet’, H. ‘ Frances Williams’ and H. ‘Francee’, decreased slightly in H. plantaginea, and did not change in H. ventricosa ‘Aureo Marginata’, H. ‘Tokudama’, H. ‘Sum and Substance’, or H. sieboldiana ‘Elegans’ as chilling duration increased. This study indicates that there is no absolute chilling requirement for shoot emergence or subsequent growth of hosta tested. All cultivars benefited from chilling with quicker shoot emergence and fewer days to first leaf unfurled, with the greatest benefits occurring between 0 and 6 weeks. However, the benefits of chilling, as exemplified by growth and vigor, varied widely among species and cultivars.