MORPHOLOGY OF BEDDING PLANTS IN RESPONSE TO LOW NIGHT TEMPERATURE AND ENERGY USE IMPLICATIONS

Seedlings of bedding plant crops were grown in greenhouses, January-May 1987 and 1989, at day air temperatures of 27 +/- 3-degrees-C (9 h) and either 7 +/- 3-degrees-C or 18 +/- 3-degrees-C night air temperatures (15 h). Morphological evaluations of the crop response to night temperatures were taken and calculations of fuel energy required to operate greenhouses at 7 and 18-degrees-C were determined. Crops which grew well at 7-degrees-C and which were short, compact and bloomed quickly were mimulus (cultivar 'Yellow Flower'), marigold (cultivars 'Aurora', 'Janie') and petunia (cultivars 'Crimson', 'Joy'). Other crops which grew well at 7-degrees-C, but took longer to bloom were geranium (cultivars 'Cardinal Orbit', 'Orbit Glow', 'Pink Elite', 'Violet Elite'), marigold (cultivar 'Perfection'), pansy (cultivar cultivar 'Universal Mix') and verbena (cultivar 'Springtime'). Crops which were stunted or took too long to bloom were impatients (cultivar 'Accent'), dianthus (cultivars 'Big Eye Crimson' and 'Scarlet', 'Magic Charm', 'Princess'), snapdragon (cultivars 'Liberty', 'Pixie') and zinnia (cultivar 'Peter Pan'). Fuel savings at 7 vs. 18-degrees-C were 9.71 of fuel oil per square meter in January, 8.8 in February, 9.6 in March and 1.8 in April.