Prolonging Poinsettias

By The Old House Web

By Jay B. Fitzgerald and Donald H. Steinegger
University of Nebraska Cooperative Extension

Poinsettias are the most popular decorative plants for the Christmas and NewYear holiday seasons. The newer cultivars often remain colorful until spring anddo not have to be discarded when they finish blooming. Following a few basicprinciples can bring the plants back into full bloom.

Prolonging a poinsettia's blooming period
  • Place the plant where it will receivea maximum amount of indoor sunlight.
  • Avoid drafts that cause rapid temperaturefluctuations and premature leaf drop.
  • Night temperatures should be no coolerthan 60?F to 65?F. Day temperatures should not exceed 80?F. Poinsettias willexperience premature leaf drop at temperatures below 55?F.
  • Keep the soil slightly moist, but not soggy.
  • When you get a poinsettia, checkto see that the soil drains adequately.
  • About two weeks after acquiring theplant, fertilize it with a complete fertilizer according to package directions. Repeat this every seven to ten days until the plant loses its brightly coloredbracts.
  • Water thoroughly and allow water to drain through the container.
  • Often poinsettias are sold in a paper or plastic sleeve, but they should notremain sleeved any longer than necessary. Ethylene gas can accumulate within thesleeve and cause premature flower drop and leaf curling. Leaf drop is a commonmalady in poinsettias.
Don't discard after Christmas: Reflowering

Many of the new poinsettia cultivars will keep their leaves and remainattractive even in summer. If the plant retains its leaves, treat it like anyhouseplant. Place it in a sunny location and apply a complete fertilizercontaining trace elements once every two weeks. As soon as night temperaturesreach a minimum of 60?F, the plant can be set outside.

If a poinsettia plant drops its leaves or is no longer attractive, let thesoil dry out and keep the plant in a cool location such as a basement windowledge; it still needs some light. The temperature should not rise above 60?Fwith about 50 to 55?F being best. Bring the plant out of its resting stage inlate April or early May and cut the stems back to about 3 to 5 inches above thesoil. If there is more than one plant per pot, separate them and replant inindividual containers.

If repotting is necessary, use a soil mix that is loose, porous, andwell-drained. Use a soil mixture composed of three parts garden loam, two partsorganic matter (peat, compost, leaf mold) and one part perlite or vermiculite.This mixture should be pasteurized at or about 180?F for 30 minutes. You alsocan buy a premixed, pasteurized media. If you are mixing your own soil, add oneteaspoon of superphosphate or bone meal for every 2 1/2 cups of soil mixture andthoroughly mix in.

After repotting, thoroughly water the plant with a fungicide solution toprevent disease infestation. Place the plant in a light, warm place and waterwhenever the soil begins to dry. As soon as the night temperature reaches aminimum of 60?F, the plant can be set outside. Place the plant in a shadylocation for two to three weeks to allow for acclimatization and to prevent leafsun scald, then sink the pot in a sunny location with well-drained soil. Givethe pot 1/4 turn every few weeks to break off any roots that might be growingthrough the drainage holes.

Once the new shoots are about 1 inch long, apply a complete fertilizercontaining trace elements. Water soluble fertilizers are easiest to use. Slowrelease fertilizer also may be successfully used -- follow label directions.Fertilize plants at seven to ten day intervals. To prevent your poinsettia fromgetting too tall, pinch off or prune the growing tips when they are about 4-6inches long. If the new shoots grow another 5 inches before late August, repeatthe process. Pruning shapes the plant to form an attractive compact growth.

When night temperatures become cool, 55?F-60?F, bring the plant indoors toa sunny location. Beginning Sept. 25, poinsettias need complete darkness from 5pm to 8 am daily. Put a cardboard box or other device over the plant to providethe "shorticulture day". Lights from any lamps will prevent normalflowering of an uncovered plant. Continue this "shorticulture day"treatment until the plant bracts show color in late November. Shorticulture daysand 60-65?F night temperatures are essential for good bract development.

Poinsettias bloom according to day length. Varieties are grouped according tothe amount of time between shorticulture days and the appearance of coloredbracts. Cultivars such as Amy and Lady will bloom about eight weeks after theonset of shorticulture days. Jingle Bells and V-14 Glory will bloom about 10-11weeks after the onset of shorticulture days. Other cultivars may responddifferently.

 

History

The poinsettia Euphorbia pulcherrima is a native to the area around Taxco,Mexico, and was introduced to the United States by Joel R. Poinsett, the firstUnited States ambassador to Mexico. Poinsettia or Euphorbia is a member of thespurge family and is characterized by small flowers (cyathia) and large,brightly colored, leaf-like bracts

The poinsettia flowers are actually small and inconspicuous. Poinsettiabracts may be either red, pink, white, yellow, or marbled; the most popularcolor is red. In their natural habitat, poinsettias bloom according to daylength.In their native locale, they are actually a large growing, woody shrub with aheight above 10 ft.

Research indicates that poinsettias contain no chemicals commonly consideredtoxic; however, we do not recommend eating the plants. While most people are notsensitive to the sap, it can cause a mild skin irritation.

 

Disease and Insect Pests

Several insects may attack poinsettias: white flies, fungus gnats, mealybugs,and spider mites. The adult white fly is easily recognized; it is covered with awhite, waxy powder and has an erratic flight pattern when disturbed. Fungusgnats are small, dark-colored flies about 1/8 inch long. They can be foundeither on the plant or soil surface. The adults are more of a nuisance, whilethe larvae tend to feed on plant tissue. Mealybugs are serious pests ofpoinsettias. These insects are soft-bodied and appear as a cottony mass, usuallyin the axis of the leaves.

Most serious diseases that affect poinsettias are soil-borne and areprimarily fungi. Species of Rhizoctonia, Pythum and Phytophthora are the mostcommon diseases. The easiest methods for controlling these disease organisms areby sanitation and periodic soil drenches with a recommended fungicide.

 

Propagation

If plants get too tall and you want to propagate them, take leafy cuttingsduring early to mid-August. Cuttings should be about 4 inches long and may berooted in any pasteurized media.

The use of rooting compounds will increase thepercentage of cuttings that will root and the rate of rooting. Place the potswhere humidity is high. A terrarium or similar structure with high humidity isan ideal location for raising poinsettias.

The leaves on the cuttings should notwilt. To prevent this, reduce the amount of leafy surface by cutting some basalleaves in half--shading the cuttings. The more light the cuttings can be exposedto without wilting, the more rapidly the rooting and the more vigorous therooted cutting. Keep the medium moist but not saturated with water. Airtemperature of about 70?F by day and 60?F by night is best for rooting.Cuttings will root in about three to four weeks. Further treatment of the rootedcuttings is the same as for plants bought from commercial sources.



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