Answer: Poinsettias are perennials in warm climate and grow outdoors in places like California and Mexico. In cold winter climates such as yours, they need to grow indoors during the winter but can be taken outdoors during the spring and summer months. Find a protected spot in your garden to help acclimate your poinsettia to growing in the great outdoors. In a week or two, gradually move it to an area where it will get full sunshine. At that time you can pinch out the tips of the stems, or cut the stems down to about 6" to encourage dense, bushy growth. In the early fall, when nighttime temperatures begin to drop to 55F, take your poinsettia back indoors.
Flowering is "photoperiodically" induced in the poinsettia. This means that flowers begin to form when the days are a certain length, or, more accurately, when the nights are long enough. The poinsettia is a short-day or long-night plant. Without long nights, this plant will continue to produce leaves and will grow but will never flower. You must make certain it receives no light from any source. Very short periods of lighting at night may be enough to prevent or interfere with flowering. Even light from a street light can stop flowering. If the plant is to be grown in a room that is lighted nightly, cover it completely at dusk (5p.m.) every day with a heavy paper bag, a piece of opaque black cloth, other light-tight cover or place in a dark closet. Flower initiation begins in late September and early October. Dark periods longer than 12 hours are necessary for flower set. Flowers mature in from 60 to 85 days depending on varieties, temperature and light intensity. Because flower initiation depends upon the length of the dark period, your poinsettia must be kept completely dark from 5 p.m. to 8 a.m. The time to give this treatment is from the end of September until December 15. Once you can see the flowers developing in the growing plants, i. e., when the floral bracts start to show definite color, it is not as important to continue giving the dark period, though it is advisable to continue until the bracts are almost fully expanded. Temperatures should be no less than 55?F at night, but not more than 70?F. During the day give the poinsettia as much sunlight as possible. Best wishes with your poinsettia.
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