The Method of Precooling to Improve Flower Quality of Forced Dutch Iris cv. Blue Magic

Abstract

It is impossible to force Dutch iris ‘Blue Magic’ early and to obtain cut flowers with long flower stalks and short leaves by using the normal method of precooling at 9°C for 9 weeks. After exposing bulbs to ethylene at 10μl/liter for more than 24hr to ensure flowering, they were subjected to precooling at different temperatures and for various durations to improve flower quality.
Flower stalk lengthened when bulbs were exposed for 3 weeks at 15°C before they were precooled at 9°C. Leaf length decreased with increasing durations of precooling at 9°C. Foliar applications of 5mM silver thiosulfate (STS) 4 weeks after planting precooled bulbs resulted in enhanced extension of flower stalks.
In conclusion, cut flower of ‘Blue Magic’ with good quality can be obtained by precooling bulbs at 15°C for 3 weeks and at 9°C for 7 to 8 weeks and then spraying the emerging leaves 4 weeks after planting with 5mM STS.