Euphorbia pulcherrima (pulcherrima meaning pretty) is native to the tropical areas of Mexico and Central America, where they grow without care, even reaching roof height! In our climate (Sacramento), the freezes turn them to mush, so they never really get the chance to grow that tall. It takes some cunning and work to keep them alive, but it is not impossible. Essentially, like other frost-tender perennials, you need to protect them from those low temperatures ... by bringing them indoors, or by creating an outdoor frost-protected area until the last frost for your area. When they finally drop their leaves, cut stems back to 2 buds and reduce water. They will soon start putting out new growth, preparing for their next blooming season, which is late winter to early spring (late January thru March). Breeders force them into an earlier bloom in December by jump starting winter and you can try it, too. In early Oct, get those faux, long-night winter nights started. Confine your poinsettia to a darkened space, like a dark closet, in the evening for 14 hours, then bring into the light for 10 hours. Do this for 10 weeks.
Since your outdoor poinsettias will probably be too large by next December, you may want to propagate new plants by making late-summer cuttings of stems with 4 - 5 eyes (joints). Then, start your winter! (See what I mean about the cunning and work?)
Here's an interesting video about the creation of a huge Poinsettia ball, from the Chicago Botanic Garden's Wonderland Express...
At this point, this is all book-learning to me. Must admit, I've never done it. But, I do have my little poinsettia pictured at the top, and I'm going to give it a go this year. How 'bout you? I've just given a brief outline of the procedure...read more in the two great references I used, Sunset Western Garden Book, and the horticultural website, Floridata.
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