Some poinsettias grow well in lower temperatures

Problem: Heating bills take a big chunk out of the profits.

Solution: Turn down the heat on the poinsettias, a typically high energy-use crop.

Details: Some breeders maintain poinsettias can be grown successfully under cooler growing temperatures as they do under standard conditions. Nora Catlin, floriculture specialist at the Long Island Horticultural Research and Extension Center, tested that theory with 32 poinsettia cultivars. Selections were primarily early- to midseason varieties.

“Growing poinsettias at a cooler temperature has promise, but you have to tweak your management a bit. The effects are varied based on the cultivar,” Catlin said.

Colors were sharper and brighter when grown at cooler temperatures, but the whites had a yellow tinge to them, she said.

From Aug. 7-25, temperatures were maintained at 65°F day and night. By Oct. 18, the temperature was changed to 75°F day and 65°F night. On Oct. 31, the temperature was lowered to 60°F day and night. By Nov. 16 the temperature was raised to 65°F day and night. On Dec. 11, the night temperature was dropped to 62°F.

The cooler temperatures caused about a two-week delay in production time, but the schedule could be tweaked by adjusting the temperature or putting the plants in a cooler house at a later date, she said.

The cooler temperatures resulted in smaller plants with smaller bracts, which may eliminate or reduce the need for growth regulators.

“Many of the cultivars were comparable to the plants grown in warmer greenhouses,” she said.

Growing poinsettias in cooler temperatures is worth considering. Her preliminary calculations showed a 20-percent difference in heating costs between the warm and cool greenhouses.

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For more: Nora Catlin, (631) 727-7850; njc23@cornell.edu.