If you are like me, you hate to throw away living things, especially beautiful flowers. Poinsettias, especially the newer types, can be saved from year to year, but the result is not always worth the effort. The blooms are not always the same quality as the original blooms. Usually, the best policy is “enjoy them and toss them.”
The bloom of the poinsettia is actually a group of tiny flowers, usually red, in the center surrounded by colored leaves called bracts. The bracts may be several different colors: pink, red, white, yellow, orange, or variegated. The plant is actually a woody shrub, and in its native habitat it could grow to over 10 feet.
Poinsettias are the most popular plant for the Christmas season, and with a little extra care (according to the University of Illinois Extension), they can be made to last several weeks. The length of time is determined by the maturity of the plant when you buy it and how you treat it.
Care:
Place the poinsettia in a sunny window
Do not let the leaves touch a cold window pane
Indoor temperatures should be from 60 to 70 degrees
Cooler temperatures at night will prolong blooming
Punch holes in the bottom so that the soil can drain
Water only when the soil is dry
Do not fertilize when the plant is in bloom
Avoid warm or cold drafts
Reflowering
You can actually get your poinsettia to bloom again next Christmas if you follow a yearlong schedule of care. Remember, before you start, the end results may not be as good a quality as the original bloom. Anyway, in early spring cut back the old flowering stems to four to six inches. This will prevent the plant from being tall and leggy, and it should promote new growth.
In late spring or early summer, repot the poinsettia into a larger pot and place it in a sunny window. Be sure to keep the soil moist. After the danger of frost, take the plant outside and place it in a shady location. Be sure to turn the pot regularly to keep the plant from growing more on one side. To be attractive, your poinsettia needs to be well rounded. You also need to follow a regular schedule of watering and feeding every two weeks with a soluble fertilizer (20-20-20).
In the fall before temperatures reach 55 or 60 degrees Fahrenheit at night, bring in your poinsettia and place in a sunny window. Don't forget to check for pests and diseases. You don't know what you may have brought inside from the yard.
Poinsettias need short days and long nights in order to produce blooms. Without long nights, they will continue to grow leaves and never bloom. Even light from a street light or a night light in your home could be enough to interfere with the flowering. Cover your plant completely or place it in a dark closet. Flowering begins in late September and early October, and the flowers mature in from 60 to 85 days depending on the amount of light and darkness and the temperature. Give your poinsettia as much sunlight as possible during the day, and continue fertilizing it until mid-December.
Diseases
Several diseases affect the production of poinsettias. Gray mold is a foliar disease that causes brown spots to form on the flower bracts. The fungus readily attacks damaged tissue and can cause significant damage to the aesthetic quality of plants. Large cankers form when stems are invaded through wounds or cracked branches. Defoliation and death of branches occur above the cankers. This mold is easily spread in greenhouses by sprinkler systems and fans. This mold must be controlled in the entire greenhouse, because plants other than poinsettias are susceptible. Plants should have ample space for air circulation, and heating and venting should be adjusted to keep the humidity low.
Powdery mildew was first seen in the U.S. around 1990. The mildew covers the plants with a powdery substance and kills the sale. It does not usually survive from year to year except in frost free climates where the poinsettia is grown as landscape ornamentals. The most effective fungicides for control of the mildew appear to be DMIs triadimefon, triflumizole, and myclobutanil (17).
Poinsettia scab is caused by the fungus Sphaceloma poinsettiae. The disease affects both leaves and stems. Small round lesions on the leaves develop white to brown centers with red or purple rims. A plant with this disease is easily detected because an infected stem will grow much longer than the others.
Pythium root rot causes crop losses every year. This disease usually attacks early in the season right after cuttings have been potted. The affected cuttings will wilt and die rapidly. The base of the cutting will turn brown and appear to be water-soaked. The plants that do survive will be stunted. They will flower prematurely and defoliate. Sources of the Pythium include contaminated soil outside the greenhouse or irrigation water reservoirs, peat moss, surface water, and even some non-soil potting media. Pythium root rot is very difficult to control once it has taken hold. Every effort must be made to prevent it. In greenhouses with a history of Pythium, fungicides or biological control agents must be applied as early in the cropping cycle as possible and several times throughout the season.
