Bringing Poinsettias Back Into Flower

Tips And Tricks For The Home Gardener

By Arlene Wheeler

Have you ever wondered how to get that poinsettia you bought last Christmas to color up once again for the coming season? It takes a little effort, but it's something the average indoor gardener is capable of doing, and the rewards are definitely worth it. You have to know what to do at each point in the season to prepare the plant for the period of darkness it has to endure in fall that actually triggers the coloration.

In Late Winter - Early Spring:

Cut back each of the old flowering stems to 4-6 inches in height. Do this in February or March to promote new growth.

In Late Spring - Summer:

Re-pot into a pot that is 2-3 inches larger than the plant is growing in. Make sure the soil mass is moistened and place it in a sunny window. When all danger of frost has passed and night temperatures are above 60 degrees F., the plant can be placed outdoors. Place the poinsettia in a shady location for two to three weeks to allow it to become acclimated to the new environment. Then sink the pot in a sunny protected outdoor flower bed. Light shade during the afternoon is OK. Turn the poinsettia pot regularly to prevent rooting through the bottom holes. It is suggested that a quarter turn each week will prevent this and will also help to keep the plant growth even all around the pot. If the pot is not turned, one side may get more sun than the other.

If you prefer a short plant with many flowers, pinch out the growing shoots to encourage branching. Pinching should produce more flowers and a nice bushy plant. This should be done at three to four week intervals, according to the speed of growth. Pinch out the top 1/4 inch by hand. Two or three large, fully-expanded leaves should be left below the pinch point. This will serve as a guide for knowing when the shoots are ready for pinching. Continue this practice until mid-August, when the plant should have a satisfactory shape and number of shoots.

Keep the plant growing actively all summer by regular watering and feeding every 2 weeks with a complete soluble fertilizer (20-20-20).

In Fall:

Before night temperatures fall below 55-60 degrees F. (10-12 degrees C.), bring the poinsettia indoors to a sunny location. Check for pests and diseases and place the plant in a south-facing window.

Flowering is “photo-periodically” 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 light 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 highly lighted, cover it completely at dusk (5 p.m.) every day with a heavy paper bag or black garbage bag, or place it 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 the variety, temperature and light intensity. Because flower initiation depends on 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 15th.

Once you can see the flowers developing in the growing plants, i.e. when the floral bracts start to show definite colour, it is not as important to continue giving this dark period, though it is advisable to continue until the bracts are almost fully expanded. Temperatures should be no less than 55 degrees F. at night, but not more than 70 degrees F. During the day, give the poinsettia as much sunlight as possible.

Reduce the amount of fertilizer given after bringing the plant indoors. Growth will be slower in the lower light intensity inside the house. High night temperatures, coupled with low light intensity, low nutrition, dry soil or improper photo period may delay maturity.

Propagating Poinsettias:

If you want to propagate your poinsettia, take leafy cuttings during early to mid August. Cuttings should be about 4 inches long and may be rooted in any pasteurized medium. The use of rooting compounds will increase the percentage of cuttings that will root and the rate of rooting.

Place the pots where humidity is high. A terrarium or similar structure with high humidity is an ideal location for raising poinsettias. The leaves on the cutting should not wilt. To prevent this, reduce the amount of leafy surface by cutting some basal leaves that are shading the cuttings in half. The more light the cuttings can be exposed to without wilting, the more rapidly the rooting and the more vigorous the rooted cutting.

Keep the medium moist but not saturated with water. An air temperature of about 70 degrees F. by day and 60 degrees F. by night is best for rooting. Cuttings should root in about 3-4 weeks. Further treatment of the rooted cuttings is the same as for plants bought from commercial sources.