Poinsettias are as symbolic of Christmas as pumpkins are of Halloween.
The poinsettia, Euphorbia pulcherrima, is a commercially important plant species of the diverse spurge family Euphorbiaceae. The species is indigenous to Mexico and was first brought to the United States in the 1820s. Also known as the Christmas Flower, it is particularly well known for its red and green foliage. The poinsettia is a tropical species of Euphorbia. In frost-free regions it is grown as a garden shrub, attaining a height of 12 feet high and 8 feet wide. However, in our colder climate, the poinsettia needs to be maintained as a spectacular potted plant.
Poinsettias, a vibrant holiday plant, are popular Christmas decorations in homes, churches, and offices. They are as much a part of the holiday season as evergreen trees. These plants are available in large numbers from hardware, drug, and grocery stores across the United States. December 12 is National Poinsettia Day to honor Joel R Poinsett and Paul Ecke Jr. who were both instrumental in developing the poinsettia industry. Today, this plant is the world’s most economically important potted plant with over 100 cultivated varieties of poinsettia.
A Flower without petals
What most people mistake as flower petals are in fact specialized leaves called bracts.
The flowers of the poinsettia are unassuming and do not attract pollinators. They are grouped within small yellow structures found in the center of each leaf bunch and are called cyathia. Flowers of this type are unique and are typical of the Spurge family.
What Makes Poinsettias Bracts Turn Red?
It is actually the plant’s specialized leaves called bracts that provide its color through a process called photoperiodism. What this really means its that, poinsettias develop vegetative growth when the photoperiod is long and flowers when the photoperiod is shorter. So a Poinsettia is what is called a short day photoperiod plant, which means that it naturally flowers when the nights become longer than the days.
In order for a poinsettia to change color, it needs 11 hours and 40 minutes, let’s just say twelve hours of darkness for at least five consecutive days. That tells the plant cells in the bracts to develop their vibrant red pigment. In commercial production, many growers use a black cloth to adjust light levels to either produce earlier crops or make the entire crop more uniform. After the color change process has taken place, poinsettias need at least six hours of indirect sunlight per day to maintain their brightest color.
Creating New Varieties of Poinsettia
Active breeding of poinsettia began in the 1950s to develop cultivars that would retain their leaves and bracts for a longer time. These breeding programs focused on stronger stems, leaf retention as well as early blooming and flower color variation. The height of this plant is also critical to sales. With the use of chemical growth retardants, the size of poinsettias can be controlled to produce 9 to 36-inch plants.
Many Plant breeders continue to tinker with poinsettias and modern technology has spawned some interesting mutations, with the use of gamma and X-ray radiation. Their efforts have translated into more color selections and better quality plants for consumers. Bract colors range from red to white, pink to burgundy, there is even an orange variety.
Quick Poinsettia Facts
- Ideal temperatures are 65 to 75° F
- Contrary to popular belief, poinsettias are not poisonous
- If you want to care for them hydroponically, an ebb-and-flow system works best
- When first introduced to the U.S. most botanists dismissed it as a weed
- Studies estimate that 80% of poinsettia sales are made by women