EFFECT OF LIGHT INTENSITY, PHOTOPERIOD AND PLANT GROWTH RETARDANTS ON PRODUCTION OF ZINGIBERACEA AS POT PLANTS

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Curcuma sp. ‘Precious Petuma’ and C. parviflora ‘White Angel’ can be grown under shade levels of up to 60% without jepordizing plant quality. Curcuma alismatifolia ‘Chiang Mai Pink’ however, should be grown under full sun and a plant growth retardant (PGR) application of 10 mg a.i./pot of uniconazole and over 20 mg a.i./pot of paclobutrazol must be used for production of a flowering pot plant. If this ginger was to be sold as a taller patio plant, PGR application could be thwarted. Postproduction longevity of the flowers of these three ornamental ginger in the greenhouse was excellent, up to 40 days. Rhizomes of ornamental gingers. were soaked in gibberellin4+7 at 0, 200, 400 or 600 mg L -1 and planted into 15.2 cm diameter containers. Gibberellin4+7 delayed shoot emergence and flowering but did not affect the flower number. Curcuma alismatifolia ‘Chiang Mai Pink’, C. gracillima ‘Violet’and C. thorelii had postproduction longevities of 4.6, 2.6 and 3.8 weeks respectively, making these three species of curcuma excellent candidates for use as flowering pot plants. Rhizomes of ornamental gingers were grown in a greenhouse under 8, 12, 16, and 20-h photoperiods. All plants grown under the 8-h photoperiod became dormant over a 15 week time period. After 90 d, most ginger species grown under the 16 and 20h photoperiods were taller than those grown under 8 and 12 h. A larger number of unfolded leaves was indicated for all ginger species grown under 16 and 20-h photoperiods compared to those grown under 8 and 12-h photoperiods except for C. thorelli. The percentage of unfolded leaves as determined by quartile indicated similar results. The number of underground rhizomes of C. alismatifolia, C. cordata and C. petiolata increased when plants were grown at 16 and 20-h photoperiods. The number of tuberous-roots (t-roots) increased as photoperiod decreased below 16 h for C. alismatifolia, C. cordata, C. petiolata, K. sp. and S. kirkii. Siphonichilus decora produced no t-roots while C. thorelii produced the most t-roots at 16 h. Vegetative growth of gingers grown in this study, except for C. thorelii, was maintained and increased at photoperiods of 16 and 20 h Photoperiods of 8 and 12 h induced dormancy and t-root production of most of these gingers.