Euphorbia Pulcherrima is a deciduous large shrub or small tree that has rich green leaves with dentate (toothed) margins. The stems and leaves are filled with milky sap that is a strong skin irritant and causes severe damage if it gets into eyes.
During winter the tips of the stems produce clusters of yellow flowers called cyathia. These are surrounded by bracts (modified leaves) that are traditionally red in colour, although many variants occur. The variants include orange, cream, white, pale yellow, pink and even green; sometimes they are variegated or marbled with combinations of two or more colours.
Poinsettias have been popular garden plants for centuries, gracing sub-tropical gardens around the globe. Joel Roberts Poinsett (1779 – 1851), the first United States Minister to Mexico, introduced the plant to the USA in 1828 and it is from his surname that the common name ‘Poinsettia’ was derived.
Today numerous hybrids and cultivars have been developed, primarily for pot culture. Dwarf compact plants are grown in glasshouses and forced into bloom through the use of dwarfing agents and controlled exposure to light. They are ‘blacked out’ for periods during summer because they require at least 12 consecutive hours of darkness each day for the bracts to take on their natural colour (and to force the formation of buds). (This physiological response of an organism to exposure to light or darkness is known as photoperiodism or photoperiodicity).
Every year millions of potted Poinsettia plants are sold as indoor decor for the festive season. The tradition of using the plants at Christmas time originated in Mexico, where Euphorbia Pulcherrima grows naturally and blooms at that time. The star-shaped arrangement of the bracts was said to represent the ‘Star of Bethlehem’ and the red colour to symbolize the crucifixion of Jesus.
Indoor Poinsettia plants can be planted out into the garden after blooming. They are generally of a much more compact habit than the normal garden types, but nevertheless become large shrubs, growing up to 2 metres tall and sometimes equally as wide.
Garden Poinsettias enjoy full sun and seem to thrive in almost any soil conditions, including poor or impoverished, dry soils. The plants should be pruned back immediately after the bracts start to drop in spring to give them sufficient time to re-grow and set flowers for the forthcoming winter season. Regular feeding with a fertiliser rich in nitrogen and potassium ensures that the plants grow lush and healthy through spring and summer, ensuring a spectacular winter display.