Keep the holiday flower power strong for next yearBy Ray Novitske, Fairfax Master Gardener
Just about everyone loves poinsettias at holiday time. But too often, this popular plant ends its days in the garbage bin sometime in midwinter. It is a sad fate for a plant that not only has a rich and interesting history, but for one that, with a little patience on the gardener’s part, is easily coaxed into rebloom.
The poinsettia (Euphorbia pulcherrima) is the best-selling potted plant in America. It is a euphorbia and a member of the spurge family. Like other members of this family, it has a milky sap. This has led to the belief that the plant is poisonous, although university research shows this to be untrue. The American Medical Association’s handbooks, however, note that ingesting parts of the poinsettia plant may occasionally cause vomiting.The poinsettia came to America in 1828 in the hands of our first U.S. ambassador to Mexico, Joel Poinsett. An amateur botanist, he found the plant growing in Mexico and brought it back to his greenhouse in South Carolina. Historian and horticulturalist William Prescott published a book on the Mexican conquest and detailed Mr. Poinsett’s discovery, naming the plant in the ambassador’s honor. By the 1900s, nurseries were selling it in California as a landscape plant and cut flower.
But the plant’s history goes back further. Aztecs used the red leaves to make a dye and the white sap as a medicinal cure for fever. Montezuma, the last Aztec king, had the plants brought into his capital city (what is now Mexico City) because the poinsettia was not grown in the city’s high altitude.
Poinsettias are native to Central America, growing in the wild as shrubs or small trees that can reach heights of 10 to 12 feet. The red blooms are actually flower bracts and leaves — not flower petals. The small, yellow cyathium found in the center is the actual flower and is typical of euphorbias.Thanks to breeders, we now have over 150 cultivars of poinsettias, with more introduced each year. In addition to red, poinsettias come in pink, yellow, orange and various shades of white. There are bicolors, variegated (marble), and speckled (Jingle Bells) cultivars. The latest cultivars to hit the market sport unusual, somewhat ragged leaves.
No matter what the cultivar, poinsettias do not like cold weather. Exposure to cold can damage the blooms and leaves. The plants prefer daytime temperatures of 60 to 70 degrees, with night temperatures no lower than 55 degrees. They also like bright light of up to six hours a day and moist, but not waterlogged, soil. Excess water will suffocate the root system.
Poinsettias will retain their beauty in the house for weeks after your holiday purchase, and thereafter, you can take steps to preserve them for bloom next year. When the red leaves begin to fade and deteriorate, cut the flowers off to about 8 inches from the soil and then give the plant a bit of fertilizer and more light. The plant should begin to produce new leaves. When the weather warms, place the poinsettia outdoors after transplanting it to a larger pot, and allow it to continue to grow.To get a poinsettia to rebloom, start early in October. It needs 12-14 hours of uninterrupted darkness each day over an eight- to 10-week period in order to form its colorful bracts in time for Christmas. Try placing it in a closet or covered by a box for 12-14 hours, and move it to bright light in the daytime. Your plant should begin fully blooming in November and December.
My own experience getting a poinsettia to rebloom was relatively easy. I kept the plant outdoors during the summer, as a foliage plant, getting a little additional enjoyment for my money. Around mid-October, it began showing signs of red color in the leaf veins and leaf stems. At that point, before the frost came, I brought it indoors and moved it to a dark basement each night after coming home from work. By the holidays, it was blooming happily, saving me both from having to buy a fresh poinsettia and from the guilt I might have otherwise felt from tossing a perfectly good plant.