What can I do to make my holiday poinsettia turn red again next year?
—Tina Golter, Brady, NE
After the holidays, continue to grow your poinsettia in a bright, sunny location. Once frost danger has passed, put it outdoors in dappled light or leave it in that sunny spot indoors. Water and fertilize to keep the plant growing actively. Cut it back in early July, leaving several strong stems, but don’t prune after that. If you’ve kept the poinsettia outdoors, wash it carefully before bringing it back into a bright indoor location by mid-September.
Starting around the third week in September, expose the poinsettia to short sunny days and long dark nights to trigger flower formation. Cover the poinsettia with a dark plastic trash bag or a box, or put it in a closet so it’s completely dark for 12 or 13 hours every night. Uncover it or bring it back to its bright location every morning.
Continue to water the soil when the surface feels dry, and fertilize at half strength about every six weeks. Within six to eight weeks bracts should begin to turn red again. (Bracts are the colorful, modified leaves that develop around the less showy “true” gold flowers.) Continue to give the plant short, sunny days and long, dark nights until the bracts are colored fully. Then put the poinsettia in its bright location permanently.
Your poinsettia is unlikely to develop as intense a color as it did when professionally grown in a greenhouse. It’s fun to give it a try, though, and it’s a great project to work on with a youngster who’s interested in plants.