Here is some great information about poinsettias thanks to Ron Wolford, Unit Educator, Horticulture and Environment at the University of Illinois. Here is a summary of his excellent article, but if you want to read it in full go to: www.urbanext.uiuc.edu/poinsettia/.
HISTORY: Joel Poinsett, the first US Ambassador to Mexico, found the poinsettia growing in Mexico. Its scientific name, Euphorbia pulcherrima, means beautiful euphorbia. William Prescott, a horticulturist, renamed the plant poinsettia in honor of Joel Poinsett. Starting in 1900, the Ecke family of California became the leading producers of poinsettias in the United States.
1. Poinsettias are not poisonous, although the white sap it produces may cause skin irritations.
2. When grown in nature, poinsettias are perennials.
3. The showy colorful parts of the plant that many call the flowers are really the leaves (bracts). The flowers are the tiny yellow things at the center of the bracts.
4. Poinsettias are the best selling potted plant in the US. 85% of all flowers sold at Christmas are poinsettias.
SELECTING A POINSETTIA:
1. There should be dark green leaves down to the soil line if possible. The bracts (leaves) around the tiny flower should be fully colored.
2. Plant should be full and balanced on all sides
. 3. Try to avoid plants that have been left in their paper or plastic sleeves; or that are pushed together & crowded on shelves.
4. Never purchase a poinsettia that has pollen from its flowers on the leaves. This indicates that the plant is past its prime.
CARE AND MAINTENANCE:
1. Protect the poinsettia from cold and wet weather when you bring it home; both of these can cause leaf damage.
2. Keep the plant in a cool bright room (70-75 degrees). If the room is too hot, the plant will not last as long.
3. Allow the poinsettia to dry out a little before watering it. A droopy plant can be saved, an over watered poinsettia will lose all of its leaves. Severe under watering will also result in leaf dropage.
4. Keep the poinsettia out of cold drafts.
5. Do not fertilize the plant as long as it’s in bloom.
GETTING A POINSETTIA TO REBLOOM OR TURN COLOR AGAIN:
1. In February or early March, cut the plant back to 4”-6” above the soil. This encourages new growth and a bushy full plant.
2. In late May or early June, repot the poinsettia into a container that is 2”-4” bigger than it’s original pot.
3. Continue pinching the plant all summer.
4. Flowering is "photo periodically" induced. That means that nights need to be long, 12 hours of TOTAL darkness; and days need to be short. Without these hours of complete blackness, the flowers will not set and the bracts will not turn color. Even the light from an outside lamp post can ruin your efforts. You will have to continue to provide 12 hours of darkness for 60-85 days so you need to start this process in the beginning of October.
5. Once the flowers form and the bracts show good color, you can put the poinsettia in its proper place in your house.