Christmas is coming and so, I decided to dedicate the Post of this week one of the most popular Christmas plants. No, I'm not speaking off a Christmas tree (however, you can find my article about Abies nordmannia,the popular Christmas tree, here), but off Euphorbia pulcherrima Willd. ex. Klotsch. from the Euphorbiaceae family. In German, this species is known as “Weihnachtsstern” (Christmas's Star). In English, the species is known as Poinsettia; named after the U. S. diplomat (and later Secretary of Defense) Joel Roberts Poinsett, who introduced the species in North America in 1825.
First of all, it's important to differ between the natural Poinsettia and the ornamental plant. The natural form is a perennial plant or evergreen shrub, which can reach heights between 90 centimeters and 3 meters (3.0 to 10.0 feet). It grows very sweeping and is one of the most sweeping Euphorbia species. However, the stalk isn't so richly branched and the internodes are very long. In contrast to this, the internodes of the breedings are shorter and the stalk is richly branched to create a dense foliage. These sorts are also smaller.
E. pulcherrima - habitus (breeding)
In both cases, the leaf bases are lanceolate to oval. They are sitting at the end of a long petiole, which is about 8 centimeters (3 inches) long. Their margin is smooth to slightly serrated. The dorsal site has a dark green color with white leaf-veins as contrast, while the ventral site is more bright green.
E. pulcherrima - leaf
As with the most Euphorbiaceae, the inflorescence of E. pulcherrima is a Cyanthium; a large, fake “flower”, which is composed of many small flowers and bracts. In this case, the actual flowers are very inconspicuous. They are small an have a yellow to yellowish green color. Petals and sepals are missing completely. Flower are either male or female. In the most cases, the flower in the center is female, while the other flowers are male (indicated by the single stamen). There are also some lip-shaped glands at the edge of each Cyanthium. They secrete nectar to attract pollinators.
E. pulcherrima - leaf veins
So, the main attraction is made by the conspicuous bracts, which surround the flowers. Basically, they have the same shape like the normal leaves but the have a bright, red color, which creates a strong contrast towards the rest of the plant. In cultivation, other colors like pink or cream-white are also popular. Blue bracts aren't naturally. In this case, the bracts are over painted with a varnish.
E. pulcherrima - bract
Flowering time is between November and February. E. pulcherrima is a short-day plant. That means, the bracts only become red, if they aren't exposed to sunlight more than 12 hours. So, it prefers shady places to grow (see distribution).
E. pulcherrima - Cyanthium with 1) stamens, 2) female flowers
and 3) glands
All parts of E. pulcherrima contain a milky, white juice, which is typical for the most (but not for all) Euphorbiaceae. This juice is a little bit toxic and can cause skin irritations and allergic reactions. However, the plant isn't deadly poisonous like some people say.
E. pulcherrima is native to Mexico and Middle America. However, it can also be found as Neophyte in Africa and the Mediterranean. The plant prefers a warm to hot climate and grows in the undergrowth of the forests with long, warm summers. It likes shady places on a moist but not wet soil. The plant is very sensitive towards light and temperature and will wilt, if it becomes to cold.
Today, the poinsettia is one of the most popular ornamental plants of the world. It was introduced to the United States by Joel Roberts Poinsett in 1825 and in Europe by Alexander von Humboldt in 1804. Since then, many different sorts and breedings were created. The plant is very popular for Christmas-themed floral displays, because the flowering time (more accurate: Dyeing of the bracts) happens during the winter months. In addition, the arrangement of the bracts reminds at the Star of Bethlehem.