A lot of poinsettias are bought as gifts and for decorating homes during the holiday season. To feed that need, growers will put about 3 percent more poinsettias on the shelves this year, the USDA estimates. But he added that consumers should look closely at the plants, because not all the crimson varieties are alike. In fact, there are over 15 different varieties of red poinsettias. Some can take high light a lot better than other types.
Light is crucial to developing the colorful bracts that encircle the tiny poinsettia flowers.
Only plants that have had at least 14 hours of uninterrupted darkness daily for 40 days will develop flowers. That requires a strict regimen for growers to time Christmas color. Even the slightest brush with light will delay flower development. Lang said understanding different poinsettia varieties reactions to day-length in the South has been a part of his research trials in the past. Some of his students this year are puzzling over certain pots in the greenhouse that seem to be reacting to light exposure, perhaps from an overhead source outside of the greenhouse, he said.