Simply continue to water the poinsettia as you would any plant, never allowing the soil to completely dry.
Now it needs to hibernate a little. So to help it go dormant, beginning April 1, gradually decrease water, allowing the soil to get dry between watering. Be careful the stem does not begin to wither. Should this happen your plant is rejecting your efforts, thus declining fast. After a couple of weeks, the plant will have got use to this drying process, so you can move it to a nice coldish place that stays around 60 degrees F (best bet may be against an outside wall, and definitely out of direct sunlight.) Water very little, never soaking or allowing it to sit in water.
About mid-May, cut all stems back to finger length (about 4 inches.) To be ready for the plant's eventual growth spurt, take this time to repot the poinsettia in a somewhat bigger container. If it is still in the plastic pot, I switch it into something more decorative, too. Take your time and water well to wake it up. Now you can bring back to the sunniest spot you have in your home, this will keep it at a temperature up to 75 degrees F throughout the summer and into September. Continue watering on a regular schedule. You should soon begin to notice some regeneration — stalks, sprouts or leaves.
You can now move your poinsettia outside for a summer blast of sunshine and temperatures. Keep it in a partially shaded location (never direct sunlight). Water regularly.
Right after July 4, take a moment and cut back each stem the length of your thumb tip. It's tempting to leave the growth, but if left uncut now, the poinsettia will grow rather leggy and lanky.
By mid-August, each branch will have new growth. Once again, pinch or cut them back to a small handful of leaves on each shoot. Now's the time to bring the plant back inside (so the temperature remains regular) and place in your sunny window. Water regularly.
To get poinsettias to re-bloom, at this point they must be limited to 12 hours or less of sunlight per day. This might sound tricky, but all you have to remember is that starting October 1 until almost the end of November, keep your plant in complete darkness from 5 pm to 8 am.
The last week in Nov. you can keep the poinsettia in the window full time. You should see several flower buds now.
Continue to water it the way you did when it was new — and enjoy as it continues to bloom throughout the season!
QUESTION: Did YOU give or receive a poinsettia this year? (Or even last year?) Say, "Me!" if you will join my mission to keep your poinsettia alive all year and see if you can "bring it back" next year!
This article was originally published as "Poinsettias: How to keep them thriving year-round" at SheKnows.com on Nov 27, 2012 by Mar Jennings. You can read the full article, which includes fertilizer information, a little history about the plant, and a blurb to make you WANT to keep the plant all year.