Influence of Temperature on Growth and Flowering of Four Meconopsis Genotypes

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University of Delaware
Meconopsis betonicifolia Franch. And M. grandis Prain are members of the Papaveraceae L. native to the Himalayan mountains. These species and the hybrids derived from them are especially prized as ornamentals for their intense blue flowers and gardenesque habit. Longwood Gardens, a horticultural display garden in eastern Pennsylvania, USA, has identified these plants as having good conservatory display qualities. However, empirical observations indicate these species are intolerant of the hot summers that occur in this geographic reason. The experiments performed in this study were designed to identify how temperature would affect plant characteristics critical to display for blue flowered Meconopsis as well as the red flowering M. punicea Maxim. Meconopsis betonicifolia, M. 'Lingholm' , a variety from the M. George Sherriff Group, and M. punicea plants were forced in the greenhouse at minimum night/day temperatures of 7.2°C /10°C, 12.8°C /15.6°C, and 18.3°C /12.1°C between December 2000 and May 2001. All plants grown in the 7.2°C /10°C and 12.8°C /15.6°C temperatures had larger canopy widths when starting to flower than those plants in 18.3°C /21.1°C environment. Plants grown in the two cooler temperature ranges also had taller flower stems, at 64.27cm and 54.44cm, for the coolest and medium environment, respectively, compared to the warmest environment at 46.27cm. The stem diameter was greatest on plants in the warmest environment at .691cm compared to the intermediate and warm temperatures at .526cm and .438cm for the medium and warmest environment, respectively. Plant dry weight was also inversely related to temperature. Plants grown at 7.2°C /10°C, at 41.8g, were 33% heavier than those grown at 12.8°C /15.6°C, at 31.4g, and 100% heavier than the plants in the 18.3°C /21.1°C, at 20.6g, at harvesting. This study demonstrated forcing temperature regulated net photosynthesis and dry weight gain of Meconopsis species and hybrids. It also showed that display quality plants with tall, strong flower stems and good foliage could be grown when temperatures were monitored and maintained at 7.2°C /10°C or 12.8°C /15.6°C and proper genotypes were selected.
Meconopsis, Blue poppy, Horticulture, Forcing temperature, Longwood Gardens