I kept a poinsettia over from last year. It was outdoors in the shade all summer and fall until yesterday. I brought it into the unheated garage. It's looking healthy, with new growth and a couple small leaves that are just beginning to turn red. What can I do now to convince it to transform into a beautiful holiday-ready masterpiece?
Unfortunately, the plant already has several strikes against it developing color by the holidays. This is because it should have received bright sunlight while outdoors, also because the plant should have begun its "training" a month ago.
Basically, in order to develop its colorful bracts, poinsettias must alternate long nights of 14 hours and short days of 10 hours for 8 to 10 weeks prior to "bloom."
The required details are described in this publication: "How to rebloom your holiday poinsettia".