How to Care for Your Poinsettia After Christmas
Poinsettias seem to follow the seasons when it comes to caring for them. During the late winter or early spring, in February or early March, these plants will need the old flowering stems cut back to 4-6 inches in height to promote new growth. During this period, the plants will also need fertilizing monthly; they will need 6 hours of light, they will need to be kept away from heat sources and the moisture must be checked daily. Water when the soil is dry.
In late spring or into the summer, repot the plant using a pot 2-3 inch larger in diameter than the one the previous one. Moisten the soil, and then set the plant in a sunny window. When all threat of frost has passed and the night temperatures are above 60 degrees, move the plant outside. The poinsettia will need to be set in a shady spot for a couple of weeks so it can acclimate to the outdoors. After the acclimation, the plant, still in its pot, is ready to place into a sunny, protected flowerbed. Turn the pot regularly to keep the plant from rooting through the hole in the bottom of the pot; a quarter of a turn weekly should be enough to prevent the rooting.
The turning will also help the plant grow evenly. Shaping the plant also takes place during this season. If you desire a short plant with many flowers, pinch the growing shoots off to produce a bushy plant with more flowers. Pinching will only need to occur every 3-4 weeks, according to how fast the plant grows. Be sure to leave 2-3 large fully expanded leaves below the pinched area for a guide to tell when the shoots are ready for pinching. Continue the pinching until mid-August. The poinsettia plant should be kept growing actively throughout the summer by watering regularly and feeding every two weeks with a complete 20-20-20 soluble fertilizer.
In the fall, before night temperatures drop below 55 degrees, check the poinsettia for pests and diseases, then brought indoors and placed in a sunny location, preferably in a south window. Reduce fertilization because the plant will begin growing slower and the plant will begin its flowering process. Poinsettia flowering is photoperiodically induced, meaning that the flowers will begin forming when the days are short and the nights are long. With this in mind, the poinsettia must not receive any light at night or the flowering will not occur.
If the plant is in a location with light, cover it with a heavy paper bag, or place it in a dark closet at dusk every day, beginning in late September or early October. Because the flower set depends on dark periods longer than 12 hours, keeping the plant completely dark from 5p.m. to 8 a.m. from the end of September to at least December 15 is very important. The dark period should continue until the floral bracts show definite color and are almost fully expanded. Temperatures should not fall below 55 degrees or go above 70 degrees and the poinsettia will need as much sunlight as possible.
If you are having trouble with your poinsettia, look at the temperatures, light intensity, nutrition, and moisture in the soil or the photoperiod method. All these can cause delayed maturity in a poinsettia.