Far re-bloom the Christmas Star (Euphorbia or Poinsettia Pulcherrima) is a green thumb and if you can you can boast of having a good feeling with plants. Indeed, despite the assurances of florists and nurserymen, far re-bloom the Christmas Star it's not easy because a lot depends on how the plant was grown.
Excessive forcing or the abuse of fertilizers to enhance color may have weakened the resistance capacity and it is not uncommon for some industrial crops to have a sort of 'planned obsolescence': Christmas stars created for to flourish a few months and then die, so they can be replaced.
Given that you have to be able to trust the florist, and that in any case the result is not guaranteed, let's try re-bloom the Christmas Star. Pass the holidays, as soon as the Christmas Star begins to lose the red bracts (which are false leaves) you can gradually reduce the waterings (which in any case must never be abundant) and when the branches are completely bare (which normally happens at the end of February) you can prune to about a palm in height.
After pruning, the pot with the Christmas Star you wish to do flourish again it should be kept in the dark for fourteen hours a day for eight weeks (about two months). Only in early May, late spring and with the arrival of the first heat, can you repot the Christmas Star with very soft universal soil and bring outdoors (always in the shade, however) returning to water and fertilize regularly and sparingly (if the water is too much, the roots rot easily)
After the summer and with the arrival of October, the Christmas Star it must be brought back to the house and placed in a very bright position to favor the coloring of the bracts. If you can do flourish again you will have been good at the plant and you can add a little red to the house for holidays without having to buy another one Christmas Star. And not just red because today you can also buy varieties of Christmas stars with bracts of different colors ranging from pink to pale yellow to white.