Environmental responses of gladioli in south-east Queensland [Australia]

Queensland production of gladiolus flowers and corms has developed into a 2.5 million-dollar per-annum industry during the last decade. Economic considerations require that flower production be regulated to meet market demand, particularly the lucrative southern winter market, whilst disease considerations require that new planting-material be provided regularly. The latter may be achieved by local production or by the usual practice of purchase at high cost (currently 22000 dollars per ha) from Victorian and South Australian producers. The present experiment provided information on number of days to flower, inflorescence, corm and cormlet yield, flower quality and vase life of 12 cultivars planted at 3- or 4-weekly intervals from February to September. Environmental conditions greatly influenced all these variables. Days to flowering varied from 77 to 132 for the various cultivar/planting-date combinations, and averaged over cultivars was greatest for the late-May planting. Degree-day summations to flowering suggested that temperature was the major factor influencing the number of days to flowering and that these cultivars were essentially day-length-insensitive for the 12.3-15.8 hour photoperiods sampled. However, flowering was severely reduced for the 11 February-18 June plantings of 'Bali Hai' and for the 26 March-18 June plantings of 'Auroa'. This may possibly indicate the existence of an environmental threshold for these cultivars. Yield and quality of inflorescences from the February to early-May plantings, which flowered in winter, were lower than from later plantings. These plantings tended to favour corm and cormlet production, which appear to compete with inflorescences for the available photosynthates.