Be sure the plant is well-wrapped when you take it outside on your trip home because exposure to low temperatures for even a short time can injure leaves and bracts. Unwrap the plant as soon as possible. Plants need air. How would you feel if you were wrapped up in plastic?!?
Poinsettias are native to Mexico, so they like to be placed near a sunny window or some other well-lit area. Keep away from cold windowpanes or drafts from radiators or fans. Room temperature shouldn’t be below 55 degrees.
Examine the soil daily and water only when it feels dry. Always water enough to soak the soil to the bottom of the pot and discard the excess water. Don’t let the plant sit in water. If you keep your plant for several months, apply a soluble houseplant fertilizer, once or twice a month according to the manufacturers recommendations.
If you plan on saving your poinsettia and reflowering it next year, follow the procedure explained below.
Late Winter and Early Spring Care
Poinsettias have long-lasting flowers – their bracts will remain showy for several months. During this time, side shoots will develop below the bracts and grow up above the old flowering stems. To have a well-shaped plant for the following year, you need to cut each of the old flowering stems or branches back to 4 to 6 inches in height. Leave one to three leaves on each of the old stems or branches – new growth comes from buds located in the leaf axils. Cutting the plant back will cause the buds to grow and develop. This cutting back is usually done in February or early March. Keep the plant in a sunny window at a temperature between 60 and 70 degrees F and water as described above. Fertilize as needed every 2 weeks.
Late Spring and Summer Care
If the plant is too large for the old pot, repot it into a larger pot.
After the danger of spring frost is past and night temperatures exceed 50 degrees, sink the poinsettia pot to the rim in the ground in a well-drained, slightly shaded spot outdoors. Remember that the plant may need to be watered more frequently than the rest of your garden. Between 15 and August 1, prune all shoots to about 4 inches, leaving about one, to three leaves on each shoot and fertilize.
Take your poinsettia plant indoors at night well before the first frost. The poinsettia can be placed back outdoors in the daytime when temperatures are warm enough or in a sunny window. Fertilize every 2 weeks. To reflower your poinsettia, you must keep the plant in complete darkness between 5 p.m. and 8 a.m. daily from the end of September until color shows in the bracts (early to mid-December). The temperature should remain between 60 and 70 degrees F. Night temperatures above 70 to 75 degrees F may delay or prevent flowering. If you follow this procedure the poinsettia will flower for Christmas.