INFLUENCE OF PACLOBUTRAZOL AND PHOTOPERIOD ON GROWTH AND FLOWERING OFGARDENIA-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 pro blems of bud abortion. Only a short short-day treatment (SDT) during h igh light irradiance months and when followed by LD gave faster flower ing, but with less induction of secondary shoots:Additional lighting d uring winter significantly accelerated flowering.