Plant Particulars December 2012
This time of year you don’t have to look very hard to find a poinsettia (Euphorbia pulcherrima). One of the most popular potted flowers in the United States, this holiday favorite is native to Mexico. This plant is named after the first U.S. ambassador to Mexico, Joel R. Poinsett who introduced it to the U.S. market in 1825. It is popular around the holidays because it naturally blooms this time of year and because of its red color.
Care of these plants starts with selecting good specimens. Choose plants with brightly colored bracts (the colorful, leaf-like structures that surround the true flowers which are shaped like yellow buttons). Be sure plants are not wilted, broken, or damaged and are free of insects and disease. White flies and aphids are especially common. Aphids produce a sticky honeydew and white flies are easy to identify as small insects whirling around when you disturb the plants.
Carefully wrap plants in a sleeve or bag to protect them from cold drafts. These warm climate plants will not tolerate even brief exposures to cold temperatures.
Once home, unwrap plants and place in cool (65°F) temperatures out of direct sunlight. This will allow plants to look good the longest. Check daily for moisture and water when soil is dry but before plants begin to wilt. Be careful to not let plants sit in water as they are often wrapped in a plastic or foil pot cover that will not allow excess water to drain away.
Most people discard their plants after the holiday season but these perennial shrubs can be grown and re-bloomed year after year. Continue to maintain plants in a bright, indirect light location indoors for the remainder of winter and early spring. Trim back stems to about 6 inches in May being careful to not get the sticky sap on you or the furniture. Repot in a larger pot with a well-drained potting soil. Fertilize and place in indirect light. Once the minimum temperature outside is above 60°F you can grow you poinsettia outside. Fertilize with an all-purpose, balanced fertilizer often. Pinch twice in the summer (early July and mid-August) to promote bushiness and control the overall size. They can get quite large. In September, bring plants back indoors to a location with bright, indirect light. To initiate new flowers, plants need to be exposed to 8 to 10 weeks of short days starting in early October to have plants in full flower by Christmas. To simulate short days, plants must be in complete darkness from 5:00 p.m. to 8:00 a.m. daily for that 8 to 10 week period. This can be done by placing plants in a dark closet, unused room or light-tight box. Any light during this time, including those from your home (even a dim lamp), will delay flowering. Plants still need a sunny place during the day. Continue to water when needed and provide plants with weekly doses of fertilizer. Once the bracts begin to show color, short day treatments can stop.
More information about poinsettias can be found in this free publication: http://www.extension.iastate.edu/Publications/RG316.pdf
With this information you can enjoy and experiment with your next holiday poinsettia!
Prepared by Aaron Steil, Education Coordinator