Interaction of Shoot Emergence Date and Long Days after Controlled-temperature forcing of `Nellie White' Easter Lilies

Abstract

`Nellie White' Easter lily bulbs (Lilium longiflorum Thunb.) were given 6 weeks of 5.5C, placed in the greenhouse, and divided into groups based on number of days to emergence: 0 to 6, 7 to 13, 14 to 20, or 21 to 27 days. At emergence, the shoots received 0, 1, 2, or 3 weeks of long days (LDs). The experiment was repeated for 3 consecutive years. Late-emerging plants had fewer days from emergence to visible bud and anthesis than early-emerging plants. Consequently, late-emerging plants flowered within 3 to 11 days of early emerging plants despite 16 to 22 days difference in emergence time. Late-emerging plants were tallest, while plants emerging in the second week had the most leaves. Flower count was not influenced by emergence date in Year 1. In Year 2, flower count decreased curvilinearly with later emergence. In Year 3, flower count was highest in plants emerging in the second week and lowest in the last week. Increasing LDs decreased the number of days from emergence to visible bud and anthesis but increased plant height. LDs did not affect leaf count in any year or flower count in Years 1 and 2. In Year 3, flower count increased with increasing weeks of LDs. LD × emergence date interactions existed, but varied from year to year.