INFLUENCE OF PACLOBUTRAZOL AND PHOTOPERIOD ON GROWTH AND FLOWERING OF GARDENIA-JASMINOIDES ELLIS CULTIVAR VEITCHII

A single application of paclobutrazol as a 12 ppm soil drench, 6 weeks after pinching, controlled vegetative growth of Gardenia jasminoides Ellis cultivar 'Veitchii' during the whole culture period and promoted flowering. Although Gardenia is usually reported to be a facultative short-day (SD) plant, induction under long-day (LD) (photoperiod 16 h; photosynthetic photon flux density of supplementary lighting 60 mumol m-2 s-1) gave significantly better flowering, more shoots, and no problems of bud abortion. Only a short short-day treatment (SDT) during high light irradiance months and when followed by LD gave faster flowering, but with less induction of secondary shoots:Additional lighting during winter significantly accelerated flowering.