Poinsettias (Euphorbiaceae pulcherrima) are everyone’s favorite plant for the Holiday Season. However, this plant doesn’t necessarily bloom naturally during the month of December. It is a photoperiodic plant and has to be tricked into flowering at the right time. Poinsettias, as well as other flowering plants such as Christmas Cactus and Kalanchoes, use a photoreceptor protein to sense when seasonal changes are occurring and nights are getting longer. By keeping these plants in total darkness for up to 14 hours a day and then placing them in bright indirect light the rest of the time, we can force them to bloom exactly when we want. With proper care you can get this popular plant to bloom in time for the Christmas season.
Joel Poinsett, our first U. S. ambassador to Mexico, introduced Poinsettias into the United States in 1825. He found them growing wild in southern Mexico. Today Poinsettias are the most popular indoor flowering plant sold in the U.S. even though they are available only six weeks of the year. The colorful parts of the Poinsettia are really modified leaves called bracts. Many people mistakenly think the bracts are the flower petals of the plant. The real flowers are the tiny inconspicuous yellow clusters found at the center of each of the bracts.
Choosing the right Poinsettia is the key to having a plant that stays colorful and beautiful the entire holiday season. Ideally there should be green leaves all the way down the stem to the soil line. The plant should be well balanced and not top heavy. The tiny yellow flowers should be barely open, and there should be no pollen on the bracts.
Whether you chose the ever popular red Poinsettia or any of the many new colors such as white, pink, salmon, yellow, marble, orange, or jingle bell, this is a lovely holiday plant that can sit on a table or be trained as a small tree; there are even hanging baskets available. Poinsettias, despite all rumors, are not poisonous, though the milky sap of the plant may cause minor skin irritations, especially for people who are allergic to latex. After Christmas, don’t rush to throw out your Poinsettia. It makes a lovely green plant all year and, with proper care, can be encouraged to “bloom” again next Christmas.
Poinsettias need very bright indirect light but no direct sun. The light from a north-facing window is really not adequate to maintain the vibrant color of the bracts. If you place your Poinsettia close to a window, be sure none of the leaves touch the glass or the cold will damage them.
Poinsettias are members of the Euphorbia family and should not be over watered. Err on the side of dryness and always allow the top 50% of the soil to dry out before watering Poinsettias. Over-watering causes green leaves to fall off, leaving bare stems topped by a few colorful bracts. Severe under-watering, in which the plant badly droops, results in both green leaves and colorful bracts dropping off. Water carefully and never allow the leaves to get wet; water, like heat and cold, mars the leaves.
Temperature is an important factor in Poinsettia care. Poinsettias last longer and look better when the temperature is between 65-70 degrees (18-22 C) during the day and about 60 degrees (15 C) at night. Temperatures that are too hot or too cold damage the leaves and may cause leaf drop. Keep Poinsettias away from drafty doors and windows, fireplaces, heaters, and the tops of appliances that emit heat.
Never fertilize a Poinsettia when it is in bloom. Six to eight weeks after pruning back your Poinsettia in the spring, begin fertilizing monthly with a plant food high in nitrogen. This helps the new leaves develop. Around August switch from nitrogen based fertilizer to a well-balanced plant food. Always dilute the fertilizer to ½ the recommended strength. Stop all feeding by September.
Although Poinsettias prefers high humidity, they still do well in the lower humidity found in homes and offices.
Whitefly, fungus gnats, mealy bugs, and spider mites are all attracted to Poinsettias, but whitefly is definitely the biggest problem. Try using Yellow Sticky Cards to trap them. If this doesn’t solve the problem, use insecticidal soap as a last resort.
Prevent fungal infections by not over watering a Poinsettia and keeping the leaves dry.
Use a good quick-draining acidic potting soil that contains quite a bit of peat moss.
Poinsettias are propagated by stem cuttings, but it is quite difficult and usually not successful when done outside of a commercial greenhouse.
Prune back your Poinsettia around the end of April or early May after it has finished blooming and rested for a few weeks. Cut it back to a height of 8-10”. This severe pruning helps produce a strong bushy plant for the coming year. The plant will initially look pretty sad but within a few weeks you’ll see healthy new leaves sprouting.
Poinsettias, despite all rumors, are not poisonous. The milky sap of the plant may cause minor skin irritations, especially for people allergic to latex.
Poinsettias are photoperiodic plants and start to develop flowers as nights become longer and days shorter. Starting October 1, Poinsettias need complete darkness for 14 continuous hours each night if you want them to bloom for Christmas. Any stray light at all, such as a tiny night-light or a streetlight, can delay or totally stop the blooming process. You may have to move your Poinsettia into a closet or even put a box over it to attain total darkness. During the day place your Poinsettia in very bright indirect light. The temperature at night is also crucial and should be between 60-70 degrees for the buds to properly set. This regimen needs to last for 8-10 weeks if you want your Poinsettia to bloom at Christmas.
Poinsettias may be used to make a beautiful centerpiece arrangement if you follow a few simple rules. As soon as you snip a Poinsettia off of the plant, soak the cut end of the stem in extremely hot water (almost boiling) for a minute and then quickly put it into cold water. This causes the milky sap in the stem to thicken and prevents wilting. You can also singe the end of the stem with a candle or match and then place the stem in cold water. It accomplishes the same purpose. After treating the stems, place the “flowers” or colorful bracts in a vase of water. Keep the vase in a cool location for about a day before using the Poinsettias in an arrangement.