Euphorbia pulcherrima, commonly called poinsettia, is sold as a potted plant throughout North America. In its native sub-tropical habitat, it is a perennial flowering shrub. The showy colored parts of the plant people admire are actually modified leaves called bracts. There are over 100 varieties in cultivation.
Common name Poinsettia, Flame Leaf Flower, Christmas Star, Lobster Flower
Poinsettias were given their scientific name by the German botanist, Wilenow. He called it Euphorbia pulcherrima, meaning "very beautiful", when he saw its brilliant color growing through a crack in his greenhouse.
The plant was given its common English name in honor of Joel Roberts Poinsett. As the U.S. Ambassador to Mexico and an amateur botanist, he brought many cuttings home to his greenhouse. The poinsettia was the most popular of them all.
Poinsettias bear dark green leaves between three and six inches long; cultivars may have pale green, cream, orange, or marbled leaves. The top leaves are a modified form called bracts. These are brightly colored - red in the species, although cultivars with pink or white bracts have been developed. The actual flowers are small yellowish structures located in the center of each leaf bunch.
In subtropical conditions, poinsettias are shrubs to small trees, growing two to sixteen feet tall.
Many Euphorbia are poisonous, but poinsettias are not, despite the myth. All parts of the plant were tested extensively at Ohio State University some 25 years ago and testing has been repeated periodically since then.
Decorative Potted Poinsettias
If poinsettias are part of your holiday decorations, you can keep them beautiful through the entire season.
Choosing the Plant
Choose a plant that has dark green foliage all the way down to the soil line. Avoid a plant with yellowed or dropped leaves.
Select a young plant. Check the small true flowers located at the base of each cluster of colored bracts. They should be fresh-looking with green or red tips. If there is yellow pollen on the flowers, the plant is past its peak bloom and the color bracts will fade soon.
Don't choose a plant that looks wilted or withered in any way.
When you take the plant out of the store, ensure it is covered with a protective sleeve if the outdoor temperature is colder than 50 degrees F.
Poinsettias prefer ample sun, so place your plant in a sunny window if possible - but don't let the leaves touch the cold window pane. Keep the plant away from drafts, whether they are warm or cold. Daytime temperatures of under 70 degrees and nighttime temperatures of 55 to 60 degrees extend the plant's blooming time.These plants are sensitive to warm night temperatures and day length. Keeping the plants in a cool, completely dark room at night will extend the flowering period.
Water the plant only when the soil is dry. Do not fertilize while the plant is in bloom
Because poinsettias are actually perennial plants, it is possible to keep them all year. Care for them as you would any house plant.
In February or March, cut each of the old flowering stems back to about five inches in length. This promotes new growth. In late April, repot them in a larger pot.
You can take them outside for the summer; if all danger of frost is gone and night temperatures are above 60 degrees. Keep them in a shaded area for the first couple of weeks. Then locate them in a spot that gets good morning sun, but some afternoon shade.
Turn the pots regularly so that the plants will not grow lopsided, leaning toward the sun. If you want a short plant with more flowers, pinch the growing shoots ever three or four weeks until mid-August to encourage branching.
Water the soil regularly. Fertilize lightly every two weeks with a balanced fertilizer.
When night temperatures start to dip below 60 degrees, check the plants for pests and bring them indoors. Place them in a sunny window; a southern exposure is best. Dilute fertilizer for each application, because lower indoor light levels will make the plants grow more slowly.
As they are very sensitive to light, they only begin to form flowers when the nights are long and cool. If they don't get enough hours of darkness, the plants will continue to grow but it will not flower. Even light from a street lamp is enough to interfere with flowering!
Around 5:00 p.m. every day, put the plants in a dark closet or cover them completely with a light-tight cover. Keep them in the dark until about 8:00 a.m. Start this treatment in late September and continue until mid-December. When the bracts show definite color, complete darkness is no longer essential.
Cool night temperatures also promote flowering. Keep the plants below 70 degrees all night long.
In Subtropical Locations
Poinsettias are hardy in USDA zones 9 to 11. They can be planted outdoors after the holidays in areas that do not experience frost. If you want them to bloom again, be careful to locate them away from street lights. Mulch to discourage the development of root rot. Cut back old growth in late winter. Pinch back shoots several times in spring and early summer to encourage heavier flower, but stop by mid-August.
They require a sunny location and will get scraggly and stop flowering if there is too much shade. They are not fussy about soil, but do require good drainage. Constantly wet locations will initiate leaf drop.
These plants can be propagated with cuttings.
Kingdom - Plantae
Division - Magnoliophyta
Class - Magnoliopsida
Order - Malpighiales
Family - Euphorbiaceae
Genus - Euphorbia
Species - Euphorbia pulcherrima
Although not poisonous, eating too many leaves can cause nausea and vomiting. However, some people are sensitive to the milky sap and may develop irritated skin after contact.