Ornithogalum dubium is a frost-tender bulbous plant native to South Africa. It is mainly grown for cut flower and flowering pot-plant production. It generally produces 10-25 cm-long flowering-stems, bearing 5-25 yellow to orange flowers with a dark green/brown center. It is in great demand in Europe and North America as a cut flower and a flowering-house pot plant. O. dubium was introduced as a new cut-flower crop less than a decade ago and is still only grown on a small scale due to its variable flower quality. The main objective of the pre sent study was to improve flowering-stem length. A three week preplanting temperarture treatment of 13°C resulted in significantly longer flowering-stems than treatments at 2, 9 or 25°C. Controlled growth-temperature and day length experiments indicated that warm day/night tempertures of 27/22°C induce early anthesis. Under this temperature combination, earliest flowering occurred under long day conditions. Stem length was maximal at moderately-low production temperatures, and long days further increased length. The number of florets per inflorescence depended on temperature. Under the two lower temperature regimes, many flowers developed per inflorescence and, again, long days enhanced this number. However under the highest temperature regime tried, this effect was reversed. Bulbs of different size were planted and even the smallest, flowered during the first year. Leaf production was proportional to planted bulb size. The rate of growth, time to flowering and total yield of daughter bulbs also depended on size of the planted bulb. Gibberellin, applied either as a preplanting dip or as foliar sprays, moderate shading (20%), as well as, a 24-h pre-planting exposure of bulbs to 10 ppm ethylene all increased flowering-stem length.

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