Growth in gardening: Regrowing poinsettias

Regrowing poinsettias for Christmases to come can be a little work but the results are worth it. PHOTO COURTESY OF JOE URBACH

Poinsettia, the Christmas Plant. As the holidays neared the plants filled the shelves of stores and garden centers all over town, the same happens every year. And every year it seems many of us spend more money buying more plants only to see them die shortly after the holidays. Why not save some money next year by saving this year’s poinsettia for next Christmas? Getting poinsettia plants to bloom again is not complicated but it does demand specific cultural controls with little room for error. Many people say it is too much work but the beautiful results you can achieve will soon convince you that the result is well worth the effort!

I will start off by assuming (this could be dangerous) that you read my last poinsettia article from a couple of week ago and that you’ve cared for your poinsettia since Christmas and that you know how to water it and that you will make sure to give it lots of light all through the coming year. Now by next September it will have grown into a small shrub and you’ll be ready to get it to bloom again for Christmas.

Here is what you do:

Short Day Plants - Poinsettia are referred to as “short day plants” and they require a night time (lack of sunlight) of 11 hours and 45 minutes to initiate flowering. So as our summer days shorten towards fall, the increasing length of night triggers flower formation. This assumes a temperature of 65 degrees Fahrenheit. If the temperatures are lower, say 62 degrees Fahrenheit, then the time of sunlight deprivation will be longer – in this example 13 hours of night. Cooler temperatures will require longer nights. And temperatures above 70 degrees will create a similar situation – too high a temperature requires longer night hours.

12 Hours - Generally, in the home environment you need night darkness of 12 hours for good and fast flower formation. And you require this night darkness for approximately six weeks starting in mid-September. After this, you only require regular day length (whatever that is in your location)

No Light at All - If you put lights onto the poinsettia leaves at night, even for a few seconds during this sixweek period, photosynthesis will start and the plant will “wake up” and the dark requirements will not have been met. In this case it will not flower. Research shows that light as low as that put out by a single candle can often trigger growth. There is some data indicating a few seconds of light will put the plant back an hour or more.

As a side note, this is why some greenhouses in urban areas can no longer grow poinsettia. Traffic moving past the greenhouses at night throw headlight beams onto the plants and wake them up and street lights can be a major problem if they don’t use artificial shading on the plants.

Full Sunshine - Getting a poinsettia to bloom again requires full, bright sunshine. Anything less will reduce flowering. In the home, this translates to a full south window or supplemental grow-lighting. Low light levels will also produce small bracts (The red or white “flower” we all think of is actually not a flower at all but is a special leaf called a brack).

Soil - Soil should be a high quality artificial mix. No garden soil as the soil has to be well-drained. Usually I recommend a good garden mix with plenty of compost but in this case I have had much more luck with an artificial mix.

Temperature - House temperatures should be in the 65-70F range during the night and 80 degrees during the day for best flowering. Remember that this is a tropical plant and so the temperature and water needs of the plant will be important.

Mat It - You might want to sit the pot on a propagation mat for the day to heat up the roots if you can’t heat up the entire room. Lower temperatures during the daytime will either impede flowering or eliminate it.

Feeding – In the last article I said that you do not need to feed the plant. That was true then, but now it is feeding time! Commercial growers feed with every watering in dilute concentrations but home gardeners can get their poinsettia to bloom again by feeding a balanced houseplant food once a week at full strength. Failure to feed will produce tiny bracts. Start feeding regularly in spring.

Pruning - Getting a poinsettia to bloom again means proper pruning in the home. The second week of September, cut all weak and spindly growth from the plant and pinch the remaining growing stems to leave four to six to leaves or leaf nodes per stem or branch. On short plants, you can simply leave four to six leaves to survive and top cut the rest of the plant off.

Humidity - Maintain a high humidity for the plant if possible. Keep feeding. The plant should throw shoots and by the third week of September, those shoots should be one inch long.

Keep feeding and watch for insects. It is at this point that whiteflies attack poinsettia and you can control them with soap only until the color starts to show on the bracts. If you spray soap on colored poinsettia leaves, they do not respond well (burning). Other common pests include mealybugs and thrips. Usually however, these pests are not much of a problem in our part of Texas.

If you maintain the temperature, full light environment, watering and feeding, you should see color by the middle of November. Any deviation from the guidelines above and flowering will be delayed.

So the schedule looks like this:

  • January through mid-September: grow Poinsettia in full sunlight, feed at least once a week and water when needed.
  • Mid-September: prune back, begin temperature regime and give 12 hours of darkness and 12 hours of full sunshine as above for at least six weeks
  • End of October: can go into full sunshine all day long with normal night time darkness.
  • Mid-November: you should start to see color in bracts
  • November: Maintain warm temperatures
  • December: enjoy you Christmas Plant!

Yes, it does seem like a bit of work but trust me, once you repot (or bump up) your plant to a larger container for next year and then for an even larger one for the Christmas after that, you’ll be as hooked as I am!

Happy New Year everyone, and thanks for your support of ‘Growth in Gardening’ this past year – 2018 promises even better article to come!

-- Joe Urbach is the publisher of and the Phytonutrient Blog. He has lived in the Central Texas area for over 30 years. Urbach is a certified Texas Master Gardener from Hays County and is currently serving as the director of training. For more information on the Master Gardener program contact the Hays County AgiLife Extension Service at 512-393-2120.

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