THE EFFECTS OF POTTING CONTAINER SIZE AND IRRIGATION FREQUENCY ON MEDIUM TEMPERATURE^©

This report focuses on the effects that potting container size and irrigation frequency has on the medium temperature and overall appearance of Senecio cineraria (dusty miller). A 7-week trial was conducted in which 20 four replicates of S. cineraria were potted into 1-, 2-, and 3-gal containers and evenly divided into two irrigation treatments: as needed (Treatment A), and on a daily basis (Treatment B). Their medium temperatures, as well as ambient and ground temperatures, were recorded throughout the trial.
Quantitative results showed that plants in Treatment A tended to exhibit higher medium temperatures, usually surpassing ambient temperatures. Results also showed that the medium temperatures of plants in 1-gal container were usually the highest ones and tended to fluctuate more than those of plants in 2- and 3-gal containers, and they also tended to exceed ambient temperatures. Finally, difference in temperature between container size was less evident for plants in Treatment B. Qualitative results showed that plants in Treatment B were bigger, more abundant, and had less dry leaves than plants in Treatment A; and that plants in 1 gal containers were the smallest and exhibited more dry leaves.
It was concluded that daily watering of S. cineraria helps to maintain their medium temperatures close to their preferred range more effectively, that S. cineraria grow faster and healthier when potted into 2-gal and 3-gal containers, and that medium temperature is ultimately dependant upon their surroundings. Recommendations include watering S. cineraria every day, potting them into containers bigger than 2 gal, and conducting further research and enhanced trials on this area.