Speaking at the HDC poinsettia meeting at Warwick HRI last week, Jack Williams, technical support at major breeder and grower Ecke Europe, said trials of Ecke's energy-efficient varieties at production sites in Europe found they could be grown effectively at an average temperature of 14 degsC.
"In our first year of trials temperatures started at an average of 18 degsC in August and September, then reduced to 17 degsC in October, 16 degsC in November and 15 degsC in December, but this year trials in Germany went further and ran at 14 degsC throughout," said Williams.
The company has produced a Bract Meter, which charts the colour development of five of its cold-grow poinsettias, including 'Freedom Red' and 'Prestige Early Red', under certain temperatures at particular days to market. Williams said: "The meter allows you to take control of your energy costs. You can adjust your temperatures to ensure you meet sales dates."
He said the benefits of cold-growing included being able to use fewer plant-growth regulators and producing more durable plants with thicker leaves and strong stems.
"Growers may need to start their schedule one to two weeks earlier to compensate for the slower rate of growth, and need to manage irrigation very effectively, perhaps using grid benches, good airflow and spacing between pots."