Poinsettias: Home for the Holidays

Ah, Euphorbia pulcherrima. The quintessential ornamental plant found in so many homes over the holiday season. These plants hail from Mexico and Central America, and are members of the Euphorbiaceae plant family, making them relatives of Croton, Castor Oil Plant, Cassava, and Rubber Tree. The plants were first discovered back in 1834, and derive their common name from the first United States minister to Mexico, Joel Roberts Poinsett. In fact, the day of his death (December 12) is now celebrated as National Poinsettia Day in the United States. Poinsettias have also been historically known under the names Mexican Flame Flower and Painted Leaf.

In the ground, Poinsettia can form a shrub that reaches up to 13 feet tall at maturity. Being tropical-climate natives, they prefer frost-free environments, but can adapt to be grown outdoors if cared for properly in many areas of the world. Due to overharvesting for the nursery trade, Poinsettia is considered to have gone extinct in many places of its native range, except in areas that are very hard for humans to access.​

A Toxic Urban Legend

In 1919, an urban legend caught fire which told of the account of a two year old being poisoned to death after consuming a single Poinsettia leaf. Solely on this basis, the plant was included in H. R. Arnold's 1944 book Poisonous Plants of Hawaii. The author admitted that the inclusion was completely based on hearsay, but that did not stop the United States Food and Drug Administration (USFDA) from circulating a publication stating completely erroneously that "one Poinsettia leaf can kill a child". All attempts to prove this toxicity scientifically have failed, however, and it is widely considered to be a safe indoor plant to keep around children and pets.

The Plant Itself

These shrubs or small trees are semi-evergreen (they generally lose most of their leaves during the cooler months of the year), and produce very small yellow flowers that are grouped together at the center of colorful bracts. These bracts are most commonly seen in bright red, but can also be pink, creamy white, variegated with multiple colors, or orange. The bracts are often mistaken for flower petals, but are actually modified leaves, colored to attract pollinators to the inconspicuous flowers.

In order for bract color to emerge brightest, these plants require some special treatment. Bract color is created through photoperiodism, which essentially means that they need long periods of darkness over a few months' time to attain their color. It is recommended that plants are kept in complete darkness for twelve to fourteen hours each day over 6 to 8 weeks for best results. In most cases, this treatment is done by growers, but for those green thumbs who keep their Poinsettias alive throughout the year for display during the holidays, this is a task that will need to be completed at home.

Picking a Perfect Poinsettia

Poinsettias are popular holiday decor in homes, churches, offices, and elsewhere across the United States, thanks to their ease of care, bright coloring, and a strategic marketing campaign by California grower Paul Ecke Sr. In 1923, he founded the Ecke Ranch, which today provides almost 80 percent of the plants bought and sold in the United States each winter. It may (or may not) be surprising to hear that Poinsettias are actually the most commonly purchased plant in the United States, with 35 million plants sold in the six week period leading up to Christmas. Having so many plants to choose from can be a bit confusing, however, so we've come up with some guidelines for purchasing these popular holiday ornamentals.

As with many plant purchases, investigating plants for health is an important step. The first indicator of a healthy Poinsettia is leaf health. Look for plants that have leaves which are a rich, dark green. Plants that have issues will exhibit leaves with burned edges, pale coloring, yellowing, curling, spots, or physical damage. These indicators can point to plant stress caused by cold temperatures, watering issues, or nutrient deficiencies. Bracts (the uppermost leaves that exhibit bright colors) should be unblemished and fully colored, without spots, curling, cracking, tearing, or dried sap.

Watering is a second major indicator of plant health. When a Poinsettia plant is picked up, it should be heavy, but not have water dripping from the bottom (unless it has just been watered). If pots are too light, make sure to check for signs of water stress (which typically exhibits itself in leaf issues, as discussed above). Heavy, overwatered pots can also cause plant stress; leaves can be wilted and yellowed due to overwatering. A plant with medium hydration is best.

Although most growers treat their plants with insecticides, bugs can find their way onto the foliage and set up camp. The most commonly encountered pest on Poinsettias are whiteflies. These pests tap into the Poinsettia's vascular system using their piercing mouthparts and extract the sweet sap from inside. 

Finding these bugs is as simple as turning over leaves and checking for them. Plants can also be lightly shaken; if a cloud of small white bugs emerges and then resettles on the plant, it is a good indicator that it has a pest problem and should not be purchased. In fact, if a plant has whiteflies, it is best to visit another store to avoid bringing any flies home with you.

Finally, choose a plant that is good lookin'! Poinsettias naturally have a handsome shape to them, and are bushy with a good amount of foliage. When looking for a perfect Poinsettia, think about the place you will be displaying it. Placed in a corner? On a narrow step? In the middle of a table? Depending on the display site, you may want to grab a plant that is a bit triangular, one-sided, or rounded.

Caring for Poinsettias

Poinsettias are considered to be easy-care plants, and when brought home should be placed in a spot that receives full sun. They can take direct sun, especially indoors. Poinsettias should be put in a spot that is not drafty; they prefer temperatures stay between 65 and 70 degrees Fahrenheit. Keep plants well-watered but take care to not overwater or have standing water around the roots. Many Poinsettias sold around the holidays have beautiful coverings around their containers for aesthetic purposes, but these coverings can cause issues when watering. They do not typically have drainage holes in them, so the water that drains out of the base of the container is captured and held, creating a situation where plants can easily drown. To water plants with coverings, make sure to remove the covering before watering, and allow excess water to drain off before replacing it.

Many people choose to throw Poinsettias away after the holiday season is finished and bract color begins to fade. However, they can also be transferred outdoors or kept inside to be used again in the future. Begin by lessening waterings; provide just enough water to keep stems from shriveling. Then, once the plant is mostly dried, cut it back to about 5 inches from the soil. Take care of the Poinsettia by providing increasing amounts of water (but still under-watering) and keeping it in a well-lighted window. It will begin to push out new growth. After the last frost of the year has passed, bring it outside.

Poinsettias in their first month outdoors should be placed in a shaded spot that is somewhat sheltered. As new growth continues to emerge, pinch it back to encourage a bushier plant to form. Over the next few months, care for the plant in its outdoor space, gradually introducing it to more and more light over time. Provide enough water to keep soil relatively moist, but not waterlogged. At around Labor Day, or as soon as nighttime temperatures begin to drop, bring the plant back indoors. Make sure to quarantine the plant away from other houseplants for a while after it is brought inside until it is clear that it has no pest or disease issues. To initiate blooms, Poinsettias will need to be exposed to between 12 and 14 hours of darkness starting six to eight weeks before the holiday season. To do this, place a box over the plant or place the plant in a dark closet. Return plants to a sunny location (one that receives between 6 and 8 hours of sunlight each day) inside a window during daytime hours when they are ready for display.

Ensure that plants get potted up about once every two years or so, depending on how quickly the root ball is growing. As a general rule of thumb, when roots start to poke out from the bottom of the pot, it is a good time to pot up. Poinsettias will continue to grow larger and larger over the years, and will be at a great size within 5 years to be planted outdoors. Make sure to harden off plants by exposing them to increasing amounts of time outdoors over a few weeks before leaving them out in the garden permanently to avoid transplant shock. The final planting site should receive direct sunlight, have well-draining soil, and be somewhat sheltered from drying winds. Another option is to grow Poinsettias outdoors in containers, so that they can be brought indoors over the cooler months of the year.

Now that you know more than you've ever wanted to know about Poinsettia plants, you're ready to care for one of your own!

​Happy Holiday Gardening.
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Resources and References

The Long, Strange Tale of the Poinsettia

Wikipedia: Poinsettia