Answer: Believe it or not, poinsettia is a perennial plant in warm regions and actually grows outdoors all year around in Mexico. Your plant will probably bloom right on schedule if you leave it where it is planted. You can dig it up and put it in a pot, but doing so could send it into transplant shock, which might delay its seasonal color. With this caution in mind, if you decide to dig it up and transplant it, water the area thoroughly the day before the planned digging. The roots have probably ventured out from the original planting hole, possibly as far out as the width of the plant. Start your digging there and work inward toward the center of the plant. After you've unearthed the plant, place it in a container and water it well to help settle the soil. I would set the pot in the same garden spot as the plant was growing, so it doesn't have to adjust to different levels of light as well as a different home for its roots.
Before night temperatures fall below 55-60?F at night, bring the poinsettia indoors to a sunny location. Check for pests and diseases and place poinsettia in a south window.
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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