Growing Guide: Poinsettia

poinsettia growing guideDownload: Growing Guide Poinsettia

Fun Facts

  • Although we think of poinsettias as small, indoor plants, in their natural habitat in Mexico, they grow into woody shrubs up to 10 feet tall.
  • December 12th is National Poinsettia Day; the date marks the passing of Joel Roberts Poinsett, the man credited with introducing the plant to the U.S. in 1825.
  • The common name is frequently misspelled, with an extra t, as in “pointsettia.” It helps to remember the name of the man the plant is named after — Poinsett.
  • Prior to the common name poinsettia, the plant was known as Mexican flame flower or painted leaf. It is known in Mexico and Guatemala as La Flor de la Nochebuena (Flower of the Holy Night).
  • According to the U.S. Dept. of Agriculture*, poinsettias are America’s number-one potted plant, with nearly 80 million sold annually, even though the market is only six weeks long each year!

Many of the plants we associate with winter celebrations are cold-hardy stalwarts, such as balsam, pine, fir, holly — even mistletoe. However, one holiday must-have stands out from this crowd: the poinsettia. Quickly damaged by frigid temperatures, this tropical beauty nevertheless graces holiday homes nationwide with its colorful bracts in shades of red, pink, and cream.

How did this chill-averse plant come to symbolize Christmas, right alongside Frosty the Snowman?

A Tradition is Born

Legend tells us that the plant’s association with Christmas began in the 1600s, when a young Mexican girl who was too poor to offer a gift in celebration of the birth of Jesus was visited by an angel, who told her to gather weeds and place them in front of the altar. The weeds transformed into the brilliant red flowers we now know as poinsettias. Soon, Franciscan friars in Mexico began including the plants in their Christmas decorations and nativity processions.

The plant’s association with Christmas would likely have remained a Mexican tradition were it not for Joel Poinsett, the first US Ambassador to Mexico. Poinsett, a skilled amateur botanist, was enchanted by the plant and brought samples back to his South Carolina greenhouses, where he began cultivating it in the 1830s.

The plant was classified as a new species and named Poinsettia pulcherrima; the genus honored Poinsett, and the species name translates to "very beautiful." Later, botanists agreed that the plant belongs in the genus Euphorbia, so it's now called Euphorbia pulcherrima, but the common name poinsettia has stuck.

Colors, Shapes, and Sizes Galore

poinsettia with open flower buds
Poinsettia with open flower buds

What we often describe as the flowers on a poinsettia are, botanically speaking, bracts. Bracts are specialized leaves that, in the case of poinsettias, change color in response to day length and surround the plant’s true flowers — clusters of small cup-like structures called cyathia, each of which is made up of one female flower surrounded by multiple male flowers plus nectar-secreting glands. The colorful bracts are there to attract pollinating insects to the inconspicuous flowers. Little is known about which insects (and possibly birds) pollinate poinsettias in the wild, though butterflies have been observed visiting the flowers.

The glorious crimson bracts inspired plant breeders to develop varieties in an astonishing range of colors, including shades of burgundy, pink, cream, salmon, apricot, and golden yellow. You’ll find bracts in marbled hues or edged in white, as well as varieties with variegated leaves. Some types have curled bracts that resemble large roses, while others have double “flowers” with layers of bracts. There are miniature forms sized for holiday tables, and tree forms with "trunks" topped by foliage and colored bracts.

blue poinsettia
A glittery blue poinsettia

But are there true blue poinsettias? Sadly, no. If you see a blue poinsettia, it’s actually a white variety that has been colored with a spray dye. Some florists and garden centers even add a scattering of glitter to further liven things up!

Choosing Plants

poinsettia with closed flowers
Poinsettia with closed flowers. Look for this when purchasing plants.

No matter what type of poinsettia you’re looking for, here are general tips for selecting plants:

  • Look for brightly colored bracts and tight yellow flower clusters in the center. The presence of dusty yellow pollen means the flowers have opened and the plant won't last as long as a plant with unopened flowers.
  • Avoid plants that show signs of wilting, dried leaf margins, or soggy soil.
  • Carefully examine plants displayed in plastic sleeves, because the sleeves inhibit airflow, which can lead to leaf drop. Although it's fine to sleeve up plants for transport, remove the sleeve as soon as possible.
  • Look for a plant with healthy foliage all the way down to the soil line.
  • Check foliage for insects, such as aphids or whiteflies.

Transporting Plants

Keep in mind that poinsettias are native to tropical climates. If you’re shopping for poinsettias and outdoor temperatures are below 50 degrees F, you’ll need to take precautions to protect your plants. Just a few seconds in freezing temperatures will damage the tender foliage. Place the plant in a loose, closed bag, and carry it quickly to a warmed-up car. Then get it home as soon as possible, taking the same care when you bring it indoors.

Caring for Your Poinsettia

Although attractive, the decorative wrapping and foil around pots will inhibit water from draining properly. Remove it, and then place the plant on a waterproof saucer or in a waterproof cachepot.

Give your poinsettia bright, indirect light for at least 6 hours per day. An east-facing window is ideal, or a south- or west-facing window with sheer curtains to diffuse the direct sunlight. Locate your plant away from cold drafts (such as near a door) and away from heating vents. Don’t allow foliage to touch cold windows. Room temperature (65 to 70 degrees) is fine.

Water your plant when the soil surface is dry to the touch. Then water thoroughly, allowing excess water to drain. Never allow the soil dry out completely or the plant will wilt. There is no need to fertilize the plant while it's on holiday display. If you intend to keep the plant after the holidays, fertilize every other time you water with an all-purpose, soluble houseplant fertilizer.

Poisonous: Fact or Fiction?

Although many people still believe that poinsettias are poisonous if ingested, studies show the risk to be minimal unless large amounts of the plant are ingested. The milky sap can cause skin irritation (especially in people with a latex allergy) so avoid handling plants more than necessary, and wash off any sap from your skin.  Use common sense and keep plants away from small children and pets that might be tempted to nibble.

To Keep or Not to Keep?

Most people grow poinsettias as annuals; that is, they enjoy them for a month or so, and then toss them when they start to look ragged after the holidays. If you’d like to try keeping yours for an encore next Christmas, you’ll need to take some specific steps.

Poinsettias are “short-day” plants  — that is, short days (or rather long nights) induce it to form flower buds and colorful bracts. Physiological changes like these that are stimulated by changes in day length are a type of photoperiodism.

Learn more: Garden How-to: Photoperiodism: Can Plants Tell Time?

  1. After the holidays, when the plant begins to drop leaves and bracts fade, trim branches back by 1/3 and allow the plant to rest by keeping it in a cool (60 degree) spot and giving it just enough water to prevent stems from shriveling.
  2. As the days begin to lengthen in spring, the plant should perk up and you can start watering and fertilizing as you would any potted plant. Place it in a sunny spot indoors. If you’d like, after all danger of frost is past, you can move it outdoors. (Transition it slowly to outdoor conditions over the course of a week or two.)
  3. About three months before you would like the bracts to color up, bring the plant indoors and start giving it 14 hours of uninterrupted darkness each day. This might mean moving it to a dark closet or using an opaque covering. Note that any interruption in the darkness negates its effect for the day. That means no peeking, no opening the closet to retrieve your mittens, etc. Give it bright light for the other 10 hours of the day.
  4. After about eight weeks, you should begin to see flower buds, and within a month, the colorful bracts you’ve been waiting for!

*https://www.usda.gov/media/blog/2015/12/01/poinsettias-helping-icon-bloom-right-time