EFFECTS OF PHOTOSYNTHETIC LIGHTING ON FREESIA GROWN FOR WINTER-FLOWERING

Abstract

In The Netherlands in winter the flower production of freesia is low and the quality of the stems is generally mediocre. In two winter seasons the possibilities of photosynthetic lighting in a winter crop of freesia cv 'Blue Heaven' were investigated. The equipment used consisted of SON-T lamps. The effects of the daily light sum (unlit, 155, 215 and 310 Wh.m-2 .day-1), lighting period (16 and 24 hours per day) and starting time of lighting on growth, yield, quality and vase life were studied. Light-integral-based and current-level-based lighting resulted in higher stem and corm production, stem quality and flowering as the daily light sum was higher. Starting at a bud length of 2 cm gave the same results as starting 3 weeks later at a bud length of 15 cm. Lighting for 24 hours per day had adverse effects on stem production, compared to 16 hours lighting (8 hours at night), whereas the effects on corm and cormlet production were favourable. Twenty-four hours lighting gave less stem yield when started at a bud length of 2 cm than at a bud length of 15 cm. As the daily light sum increased the percentage of visible leaf necrosis also increased. In conclusion, results show that light-integral-based and current-level-based lighting till a lightsum of 200 – 225 Wh.m-2.day-1 offered most prospects for freesias grown in the winter. To start with lighting was only usefull at a bud length from 15 cm. Twenty-four hours lighting in an early stage was disadvantageous.