by Amanda Wilkins
If you are curious about other plants associated with Christmas, join us for “The Botany of Christmas” with Fried Nation on Friday, December 15, from 2-4 p.m. Learn more here
Nothing says the Christmas season like a brilliant, red Poinsettia. All the big box stores seem to have had just a few of them available before Thanksgiving for those eager beavers who just love starting Christmas early (those folks have probably been enjoying the trickling stream of holiday tunes on some of the radio stations too…). But, what is it about these incredible plants that makes us associate them with the Christmas season?
Most folks would probably say it’s the beautiful red color of the poinsettias that complete the classic Christmas look. Nowadays there are more than 100 different cultivars (“cultivated varieties”) that come in varying shades of white, pink, red and everything in between. Even still, red is still the number one seller, which makes sense because it blends in with most Christmas color schemes!
Bringing the botany back in: One of the coolest parts of this plant is that the red (or white or pink, if that’s your style) “petals” are really colored leaves called bracts. The true flowers are actually those weird yellow things in the middle. If you got out your handy-dandy hand lens and took a closer look, you’d really see how alien those flower look! Anyway, so the “petals” are colored leaves in poinsettias, and this is a common characteristic in the family Euphorbiaceae that stems from the loss of true petals due to adaptations to harsh environmental conditions and other evolutionary factors. Many other species in the genus Euphorbia have been able to bring their “petals” back too. Isn’t botany fun?
The scientific name of poinsettias might also help us answer our question though. Scientists would call them Euphorbia pulcherrima Willd. ex Klotzsch, meaning “very beautiful Euphorbia” in Latin. It’s important to note that there are more than two thousand species in the genus Euphorbia, so it’s good to know we picked the “very beautiful” one!
The other answer to what makes us associate poinsettias with the Christmas season is that they naturally bloom this time of year; and what botanists mean by “this time of year” is short days and long nights. Poinsettias are particularly sensitive to light and the length of the night. You may have heard the old wives’ tale of “putting your poinsettia in the dark will make it flower”. Now don’t go sticking your poor plant in a closet to make it flower again! What the tale speaks to is the importance of long “nights” to inspire flowering in poinsettias. I remember listening to the painstaking lectures in university talking about short day, long night plants; and how the presence of any light during those “long nights” could actually break the “night” and make the plant’s internal clock start over. For a poinsettia grower, this is critical to understand because if you don’t you can have a house full of beautiful plants with no color!
Modern horticultural science has taken the humble poinsettia to the next level though. Poinsettias in the wild are tall, spindly shrubs native to Mexico. Native plants possess red bracts, but they tend to be in a sparse whorl around the yellow flowers, and are thin and not nearly as brightly colored. Through modern breeding techniques and meticulously-controlled greenhouse production, growers are able to bring bushy, dwarf, uniform, brightly-colored plants to a shelf near you (although, heaven forbid when they’re covered in glitter!). Poinsettia production starts all the way back in March when most growers order their plugs from seed companies, and the growing really gets going in October with very specific light, fertilizer and plant-growth-regulator regimes. If you want a sneak peek, check out a grower guide here: https://www.ballseed.com/PlantInfo/?phid=050005990004054.
I get asked a lot about whether poinsettias are poisonous or not. The short answer is ‘Yes, they are, if any part of the plant is ingested.’ Poinsettias are in the family Euphorbiaceae, the spurge family, which explains why you’ll see white “milk” dripping when you accidentally brush by the plant and break off one of the leaves. It’s this sap that is full of alkaloids, and it can cause some mild skin irritation in sensitive people and nausea and vomiting in pets and humans if ingested. That being said, you’d have to eat hundreds of leaves to actually die from poinsettias. You’d probably stop eating after the first bite though, because those alkaloids make the plant’s parts so bitter it deters most animals from munching. But, if Fido takes a bite he’ll probably just be pretty ill. The best you can do is make sure the plant is out of reach of pets, and children are not at risk of brushing by it and damaging the plant. If you do break a part off, just wash the sap off with a mild soap. Trust me, there are some nastier members of the family!