Background:

The poinsettia (Euphorbia pulcherrima), one of the most popular winter holiday plants, is a native to the area around Taxco, Mexico. Joel R. Poinsett, the first United States ambassador to Mexico, introduced it into the United States. In Mexico, poinsettias grow to be large woody shrubs, often reaching heights above 10 feet.

Poinsettia is a member of the spurge family and is characterized by small, inconspicuous flowers (cyathia) and large, brightly colored, leaf-like bracts. Poinsettia bracts may be red, pink, white, yellow, speckled or marbled; the most popular color is red.

Poinsettias are often thought of as poisonous, but research indicates that poinsettias contain no chemicals commonly considered toxic; however, eating the plants is not recommended. While most people are not sensitive to the sap, it can cause a mild skin irritation.

Care:

• Place the plant where it will receive a maximum amount of indoor sunlight.

•  Premature leaf drop is one of the main problems in poinsettia care. The plant needs to be kept out of drafts, as rapid temperature fluctuations will cause premature leaf drop. Even touching a cold windowpane can cause injury to the bracts. Night temperatures should be no cooler than 60 to 65 degrees F. Day temperatures should not exceed 80 degrees F.

• Another cause of leaf drop is wilting. The soil must be kept slightly moist but not soggy. Water thoroughly and make sure the pot has good drainage. Empty out any water that may be left in the pot saucer after watering.

• Fertilization is typically not needed for the first month because the potting mix includes a slow-release fertilizer. After the first month, fertilize once every two weeks until the plant loses its brightly colored bracts.

• Always remove any paper or plastic sleeve. Ethylene gas can accumulate within the sleeve and cause premature flower drop and leaf curling.

• Many of the new poinsettia cultivars will keep their leaves and remain attractive even in summer. If the plant retains its leaves, treat it like any houseplant. Place it in a sunny location and apply a complete fertilizer containing trace elements once every two weeks. As soon as night temperatures reach a minimum of 60 degrees F, the plant can be set outside.

Reflowering:

Once a poinsettia plant drops its leaves, let the soil dry out and keep the plant in a cool location--it still needs some light. The temperature should not rise above 60 degrees F; between 50 and 55 degrees F is ideal. In late April or early May, bring the plant out of its resting stage. Cut the stems back to about 3 to 8 inches above the soil. If there is more than one plant per pot, separate them and replant in individual containers.

If repotting is necessary, use a soil mix that is loose and porous. A soil mixture composed of three parts sterilized soil, two parts organic matter (peat or sterile compost) and one part perlite or vermiculite works well. You also can buy a premixed, pasteurized media. If you are mixing your own soil, add one teaspoon of superphosphate or bone meal for every 2 1/2 cups of soil mixture and thoroughly mix in.

Place the plant in a light, warm place and water whenever the soil begins to dry. As soon as the night temperature reaches a minimum of 60 degrees F, the plant can be set outside. Place the plant in a shady location for two to three weeks to allow for acclimatization and to prevent leaf sun scald, then sink the pot in a sunny location with well-drained soil. Give the pot 1/4 turn every few weeks to break off any roots that might be growing through the drainage holes.

Once the new shoots are about 1 inch long, apply a complete fertilizer containing trace elements. Use either a water-soluble fertilizer or a slow-release fertilizer -- follow label directions. Fertilize plants at seven to ten day intervals. To prevent your poinsettia from getting too tall, pinch off or prune the growing tips when they are about 4-6 inches long. If the new shoots grow another 5 inches before late August, repeat the process. Pruning shapes the plant to form an attractive compact growth.

Poinsettias are short-day plants, which means they flower about 10 weeks after the daylight shortens to 12 hours or less. For Christmas bloom, the plant must be kept in full darkness between 5 p.m. and 8 a.m. from early October until late November. Flowering will be delayed if there is any exposure to light during those hours. The plant can be put in a sunny window during the day hours. Fertilizing should continue until mid-December.

Disease and Insect Pests:

Several insects may attack poinsettias: white flies, fungus gnats, mealybugs and spider mites. The adult white fly looks like a small fly covered with white powder. Fungus gnats are small, dark-colored flies about 3 mm (1/8 inch) long. They can be found either on the plant or soil surface. The adults are more of a nuisance than a real problem, but the larvae do feed on plant tissue. Mealybugs are serious pests of poinsettias. These insects are soft-bodied and appear as a cottony mass, usually in the axis of the leaves. Gently cleaning the leaves with alcohol on a swab can control mealybugs, aphids and spider mites if caught early. Other choices for control are a variety of sprays. Read the labels carefully before using.

Most serious diseases that affect poinsettias are soil-borne and are primarily fungi. The easiest methods for controlling these disease organisms are by sanitation and periodic use of a fungicide.

Propagation:

If you want to propagate poinsettia, take leafy cuttings during early to mid-August. Cuttings should be about 4 inches long and may be rooted in any pasteurized media. 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 cuttings should not wilt. To prevent this, reduce the amount of leafy surface by cutting some basal leaves in half--shading the cuttings. 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. Air temperature of about 70 degrees F by day and 60 degrees F by night is best for rooting. Cuttings will root in about three to four weeks. Further treatment of the rooted cuttings is the same as for plants bought from commercial sources.

Adapted from a fact sheet published by University of Nebraska Cooperative Extension, Institute of Agriculture and Natural Resources. Authors Jay B. Fitzgerald and Donald H. Steinegger.