In the most mild of climates, it is possible to grow poinsettias in the ground. But if the temperatures dip below 40F, the plants will be damaged. If snow or freezing temperatures are normal in your garden, don’t plant them outdoors, but take them outdoors in the summer. Here’s one way to keep poinsettias from one year to the next, starting from shortly after the holidays.
Prune the stems back to stubs about 4 inches high. Put the pot in a cool, shady area of the house and keep the soil almost dry.
When spring arrives and it’s warm enough to put your houseplants outside, it’s time to deal with this plant again. Repot it into a pot slightly larger than the one in which it had been planted. Put it into the garden in a slightly shaded area, sinking the pot into the soil to help keep it from drying out. As soon as the temperatures begin to cool down in the very early fall, bring it back indoors.
Now, life gets a bit complicated. Put it into a very sunny location until sometime in September or early October, when you will place it in total darkness for 13-14 hours every night. This is really important. If you have a room that is not lived in at all, it can stay there. But if that room is exposed to any light whatsoever, it won’t work. If that’s the case, it must be moved from darkness (such as a dark closet) into light every day—faithfully.
When the bracts have colored again, bring them out and start bragging.