Growth and flowering responses of<i>Canna</i><i>generalis</i>to nitrogen supplied to the growing medium via top- or sub-irrigation

Abstract

SummaryEffects of nitrogen concentration on growth and flowering were studied in Canna generalis L. H. Bailey ‘Tropical Rose’ and ‘Tropical Red’ grown with irrigation supplied either to the top (top-irrigation) or the bottom surface (subirrigation) of the growing medium. For ‘Tropical Rose’, maximum total dry weights occurred at 4 mM N for both irrigation methods, but growth was greater with subirrigation compared to top-irrigation. For ‘Tropical Red’, maximum total dry weight occurred at 4 mM N under subirrigation, and 8 mM N under top-irrigation. Growth was reduced in all treatments when growing media EC exceeded 1.25 dS m–1. Shoot dry weight increased as leaf N content increased from 0.6% to 1.4 %. Plants under top-irrigation took longer to flower than did those under subirrigation. At 4 to 32 mM N, regardless of irrigation method, plants flowered after 9–10 leaves had been formed. Plants grown at 0 mM N did not flower after treatment for 145 d. Maximum spike length and floret number were observed at 4 mM N in both irrigation treatments.