Location and Temperature:
The poinsettia thrives on indirect, natural daylight, and exposure to at least six hours daily is recommended. If direct sun cannot be avoided, diffuse with a light shade or sheer curtain. To prolong the bright color of the poinsettia bracts, daytime temperatures should not exceed 70 degrees F. Avoid placing the plants near drafts, excess heat, or the dry air from appliances, fireplaces, or ventilating ducts.
Water and Fertilizer:
Poinsettias require moderately moist soil. Water the plants thoroughly when the soil surface feels dry to the touch. Remove the plant from decorative pots or covers, and water enough to completely saturate the soil. Do not allow it to sit in any standing water; root rot could result which could kill the plant. It is not necessary to fertilize the poinsettia when it is in bloom.
Outside Placement:
Since poinsettias are sensitive to cold weather, frost, and rain, outside placement during the winter months should be avoided. However, in mild climates, an enclosed patio or entry way may be suitable, provided the night temperatures do not drop below 55 degrees F. Make certain the delicate bracts are well protected from wind and cold rain.
After the Holidays:
Keep the plants in indirect sun and water regularly. Place your plants outdoors, where they can bask in the warmth of spring and summer, after outside night temperatures average 55 degrees F. or above. When the bracts age and lose their aesthetic appeal, usually by late March or early April, cut the poinsettia back to about 8 inches in height. By the end of May you should see vigorous new growth. Continue regular watering during the growth period. Fertilize every 2 to 3 weeks throughout the spring, summer, and fall months with a well-balanced, complete fertilizer.
Around June 1, you may transplant your poinsettia into a large pot. Select a pot no more than 4 inches larger than the original inner pot. A soil mix with a considerable amount of organic matter, such as peat moss, is highly recommended. If you wish, you may transplant the poinsettias into a well- prepared garden bed. Be sure the planting bed is rich in organic matter and has good drainage. Pruning may be required during the summer to keep plants bushy and compact. Do not prune after September 1.
Re-flowering:
The poinsettia is a photo-periodic plant, meaning that it sets bud and produces flowers as the autumn nights lengthen. The plants will naturally come into full bloom during November or December, depending upon the flowering response-time of the individual cultivar. Timing the bloom to coincide closely with the Christmas holiday can be difficult without the controlled environment of a greenhouse. Stray light of any kind, such as from outside street lights or household lamps, could delay or entirely halt the re-flowering process.
Starting October 1, the plants must be kept in complete darkness for 14 continuous hours each night. Accomplish this by moving the plants to a totally dark room, or by covering them with a large box overnight. During October, November, and early December, the plants require 6 to 8 hours of bright sunlight daily, with nighttime temperatures between 60 and 70 degrees F. Temperatures outside this range may delay flowering. Continue the normal watering and fertilizer program. Following this regime for 8 to 10 weeks should result in a colorful display of blooms for the holiday season.