CO-Horts Blog

Wednesday, December 31, 2014

The Great Poinsettia Experiment (that failed)

Posted by: Alison O’Connor, Larimer County Extension

I’m sure you’ve all heard the warnings about poinsettias—don’t let them dry out, don’t let them get cold, be sure to buy them on a warm day so they don’t suffer from cold injury as you walk to your car. There are a lot of care instructions that accompany that gorgeous red, pink, white or bi-color holiday plant. But are poinsettias as wimpy as we think they are? Do they really wither with a slight cold breeze? Can they withstand freezing temperatures? This is what I wanted to find out, so with my $0.99 poinsettias I purchased after Thanksgiving (yes, it’s a deal and no, the grower doesn’t make any money), I essentially tested the limits of these colorful plants to see how far I could push them.

Poinsettias (Euphorbia pulcherrima) are a member of the euphorbia family, which means they are related to leafy spurge (ugh), castor bean (highly poisonous), croton and the rubber tree. It also means they contain a milky white sap that oozes when plant parts are broken and discourages grazing animals. The scientific name comes from Euphorbus, named after the Greek physician who cared for King Juba II (50 B.C. to 19 A.D.) Pulcherrima translates to beautiful or handsome. Many of the euphorbia plants are attractive with colorful bracts (like the poinsettias) or leaves (croton).

But back to the experiment... Like you, I take extreme caution when transporting poinsettias from the store to my car and place them in my home in a non-drafty location. I water them regularly and make sure the water drains from the plastic sleeve surrounding the pot. The poinsettias do surprisingly well in my home, even though we keep our heat around 60 degrees, and last for several weeks past Christmas. Usually I get sick of watering and caring for them and they end up in the trash before they start to fade. But as I mentioned above…all those warnings! Do these plants need to be babied as much as we think?

So I bought 15 poinsettias and put them in the greenhouse and started the treatments: drowning (sitting in standing water constantly), drought (no water) and placed in a drafty spot. I looked at treatments using plastic sleeves when the plants are outdoors and no plastic sleeve (to try to determine if the plastic sleeve does anything when you walk outside). I put the sleeve and no sleeve plants outside when it was a balmy 21 degrees outside and left them there for 12 minutes (figuring that’s a long time for a person to walk from the store to their car).
The poinsettia treatments (3 reps per treatment)
In short, you can probably guess which ones looked the worst. Yes, the drowning and drought bit the dust, but it took them a few weeks. Clearly, water…either too much or too little…is not a friend of the poinsettia. The plants put outdoors looked fine. In fact, they showed no signs of cold stress at all. They didn’t even flinch! The plants put in front of the draft were also fine, but after four weeks, they were much smaller in size than their counterparts. Interesting!
'Nuff said. No water for 4 weeks.

Sitting in standing water for  4 weeks.
Plants in a drafty spot were much smaller in size.
Cold treatment (12 minutes at 21 degrees) did not affect these poinsettias.

Sleeve or no sleeve. Poinsettias appeared to be unaffected by cold.
Because I was bound and determined to see something on how cold weather affects poinsettias, I did another round with new plants. These were generously donated from the CSU student poinsettia sale (thanks Mike and Dr. Newman!). A couple weeks ago it was horribly windy and very cold. Perfect! The wind was howling at 30mph and it was 32 degrees outside. I left them outside in these elements for 20 minutes—much longer than I would have lasted…and I’m not a Zone 10 plant.
Experiment 1b,...wind and cold.
Again, nothing! No damage to the bracts from the wind. No leaf tattering. No signs of stress, except for maybe a bit of leaf tip burn.
Maybe tip burn? But this could be from fertilizer, water and/or cold.

I’m impressed. And flummoxed. My conclusion to the Great Poinsettia Experiment? They appear to be much tougher than we give them credit for. And quite scrappy. It’s no wonder that they are so popular and over 34 million are sold in the United States each year. In fact, it’s the number one potted plant (take that, Easter lily). My hat’s off to you, poinsettia. 
Maybe snow would have been a good treatment...


  1. Susan K in Green BayJanuary 1, 2015 at 1:37 PM

    As usually, another fun and instructive lesson in horticulture. Yours and the garden professor always teach me something new. I live in Wisconsin. I would bet that every poinsettia I've bought in the 20 years I've lived here were chilled when I brought them home. I never took great pains to protect them, so your research agrees with my personal experience. But I know that I've killed more than a few by overwatering, because those pretty red plastic sleeves usually dont have holes for drainage, which I forget. Thanks for dong this very interesting study.

  2. That is great! I transported 20 poinsettias(6" pots) in a VW bug 120 miles many years ago from the greenhouses at Mizzou as Christmas presents. All made it with conditions of blowing vents and very, very crowded conditions to say the least. They all survived beautifully as I worried about their outcome for 2.5 hours!

  3. I enjoyed reading this! And, good to know a person doesn't have to baby them! My mom overwinters hers every year and then plants them in her shade garden for the season.
    Thanks for the fun reading...

  4. Very informative and learned a lot about these beauties. And I wouldn't call the Experiment a failure by any means!

  5. Brilliant post!! You make learning so much fun!!
    - Deryn

  6. Most people treat the poinsettia (also called Christmas star, Mexican flame leaf, or lobster plant) as an annual, purchasing a new plant at the beginning of the traditional winter flowering period and discarding it at the end.
    Euphorbia Pulcherrima Euphorbiaceae house Plant Care