   All About Poinsettias - December 27, 2000 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County During the holiday season, we see poinsettias everywhere. Many of us buy a plant for decorative touch or as a gift for someone we are visiting. The poinsettia industry has grown around this holiday tradition. Today, poinsettias are one of the most important floricultural crops produced in the United States. Grown primarily as a potted plant for the Christmas season, total U.S. poinsettia production was valued at $66 million in 1980. This striking foliage plant was first cultivated by the Aztecs of Mexico and highly prized by Aztec Kings Netzahaulcyotl and Montezuma. After the arrival of the Spanish in Mexico, Franciscan priests in began using the plants in religious processions because of its brilliant color. Joel Robert Poinsett, the first U.S. Ambassador to Mexico, introduced poinsettias to the United States in 1825. Poinsett was a botanist and had specimens sent back to his greenhouses in South Carolina. Ponsett also distributed plants to botanical gardens and nurseries. From here, the cultivation of poinsettias grew into the holiday tradition (and major nursery crop) we enjoy today. The poinsettia (Euphorbia pulcherima) does not have showy flowers. Rather, the bracts (modified leaves) create the splash of color during the holiday season while the true flowers are small and insignificant (unless you are another poinsettia). The colorful foliage of poinsettias is a response to photoperiod (hours of daily sunlight). There are so many shapes, sizes, and colors of poinsettias available that a complete column could be written on that subject alone. Contrary to popular belief, poinsettias are not poisonous. Ohio State University conducted research on the poinsettia plant effectively disproving the charge that the poinsettia is harmful to human and animal health. Of course, the poinsettia, like all ornamental plants, is not intended for human and animal consumption. Here are some hints to keep your poinsettias looking perky and colorful well beyond the holiday season. Poinsettias thrive on bright, sunny natural daylight; at least six hours daily is recommended. Placement near a sunny window is ideal. To prolong the bright red of the bracts, temperatures ideally should not exceed 70° F during the day, or fall below 65° F at night. Be sure to avoid placing the plants near drafts, fluctuating air currents, excess heat and dry air from appliances, fireplaces or ventilating ducts. Chilling injury will occur if poinsettias are exposed to temperatures below 50° F. Frost will kill them. Poinsettias do best with a moist soil condition, not too wet and not too dry. Water the poinsettia thoroughly when the soil surface feels dry to a light touch. The best indication of a thorough watering is when the water begins to seep through the drain holes at the bottom of the inner pot. Be sure to discard any excess water, as poinsettias left sitting in water may suffer from permanent root-rot damage. It is not necessary to fertilize your poinsettias when they are in bloom during the holiday season. However, after 6-8 weeks, a balanced, all-purpose household plant fertilizer mixed ½-strength will help maintain the rich, green foliage color and promote new growth. Repeat once more in another 6-8 weeks. Here are some tips for those that would like to keep their poinsettia growing until next holiday season. At the end of April or early May, when the bracts age and begin to turn a muddy green, cut the plant back to about 8 inches. The amount you cut from the top will depend on the shape of the plant. After you cut the plant back, it will probably look rather stark, with bare branches and bluntly cut woody stems. This is not the plant's most attractive state, but by the end of May you will see vigorous new growth as the plant develops more lush green foliage. Keep the plants near a sunny window. You may place your plants outdoors where they can bask in the warmth of summer when the outside night temperatures are warmer. Continue to water the plants regularly during the growing period. Fertilize every 3 to 4 weeks throughout the spring, summer and fall months with a well-balanced fertilizer mixed ½-strength. Around June 15th you may wish to transplant your poinsettias into larger pots, about 2" to 4" bigger than the original inner pot. Use a soil mix that incorporates a considerable amount of organic matter such as peat moss. Immediately after transplanting, be sure to water thoroughly. The plants will naturally come into full bloom during November or December depending upon the flowering response time of the particular variety. This can be tricky to do outside of a controlled greenhouse environment, because any stray artificial light such as that from a street light, pool light or household lamp could delay or halt the re-flowering of the plants. Starting October 1, the plants must be kept in complete darkness for 14 continuous hours each night. Moving the plants to a dark room or placing a large box over them can accomplish this. During this period, the plants require 6 to 8 hours of bright sunlight and night temperatures between 60° and 70° F. If the temperature is too high or too low, the setting of the flower buds may be delayed or halted. The blooming process may also be delayed or disrupted by any stray light that may shine near the plants during the critical darkness period. Keep this up for 8 to 10 weeks for full color development. If this sounds like a lot of work, it is. It certainly gives me a healthy respect for the nursery industry. By the way, the NEW Yavapai County Cooperative Extension Gopher Control web site is finally up and running at http://ag.arizona.edu/yavapai/anr/hort/gopher/gophercontrol.html . I hope you all have a happy new gardening year! |