Native to Mexico, poinsettias (Euphorbia pulcherrima) are the most recognizable potted plants during Christmastime. They are popular decorative houseplants and holiday gifts in the early winter, ranging in color from white to pinks and reds. Poinsettias are usually short-lived in most people's homes, but they're better cultivated and grown in greenhouses, where temperatures, humidity levels and other environmental factors are more easily controlled. With the right conditions and care, poinsettias can grow up to 5 or 6 feet tall and wide, offering colorful foliage and blooms year after year.
Re-pot your poinsettias into planters that have drainage holes in the bottom and are about 2 to 4 inches wider than the nursery containers. Use a well-draining, all-purpose potting soil.
Keep temperatures in your greenhouse steady between 65 and 70 degrees Fahrenheit during the winter. Avoid placing the poinsettias near greenhouse doors or anyplace where they will be exposed to drafts or dramatic temperature variations.
Position the poinsettias in the greenhouse where they can receive bright indirect light for six to eight hours each day.
Water your poinsettias once every three or four days, only when the top 1 or 2 inches of soil feel dry to the touch. Mist the poinsettias daily to keep a higher level of humidity around the plants.
Feed the poinsettias once each month during the active growing season with a liquid houseplant fertilizer diluted at half-strength.
Move the poinsettias into a well-ventilated, low-light area in your greenhouse after the plants lose their leaves and begin their dormant season. Keep temperatures at 60 degrees, stop fertilizing and cut back on watering to once every month.
Cut the poinsettias back, leaving only the healthiest branches in the early spring. Set the plants back out into bright light and begin watering and fertilizing them again regularly.