Red, pink, pink or white: the poinsettia is the most popular indoor plant in Germany second only to the orchid, even though Euphorbia pulcherrima is mainly used for Christmas decorations in this country. According to the marketing initiative of the European poinsettia breeders, Stars for Europe, around 32 million specimens are sold in Germany every year. More than 700 plant nurseries produce poinsettias in this country.

In nature, the Christmas Star, as the plant is also known, is a perennial evergreen shrub that can grow up to four meters high. The plant, which originally comes from Mexico and South America, is cultivated exclusively in greenhouses in this country and tends to grow rather small. It is particularly popular because of its strikingly coloured bracts, which are the result of breeding. The actual flowers sit in the middle of the leaves and are small and rather unspectacular.

Warmth make white leaves even whiter

Despite numerous new breeds: The red poinsettia is the most popular at Christmas time, 80% of the poinsettias bought are classically red. But the white specimens, which are the result of random mutations in the genetic make-up, are also becoming increasingly popular. Following this trend, breeders from the Bavarian State Institute for Viticulture and Horticulture (LWG) in Veitshöchheim near Würzburg have investigated the influence of the greenhouse temperature on the purity of the white bracts. The result: the warmer it is, the whiter the bracts are. Temperatures of 20 degrees Celsius are therefore ideal for cultivating the white poinsettias: the leaves have virtually no other colors mixed in.

To ensure that the poinsettias are on sale in time for the holiday season, cultivation must begin in summer. Breeding specimens with unusual colors is particularly time-consuming. The LWG researchers have therefore examined the extent to which energy can be saved when growing white poinsettias in a greenhouse. Tests showed that a reducing the temperature by as little as three degrees resulted in energy savings without endangering the growth and color purity of the white species.

Bright and warm locations preferred

One thing is for sure: Euphorbia pulcherrima is more than just a Christmas plant. It is robust and long-lived, and with the right care, it can flourish until the next Christmas season. The plants love bright and warm locations. They are most comfortable at temperatures between 18 and 20 degrees Celsius. A light pruning is also good. However, poinsettias do not like draughts, cold or too much moisture. However, according to experts, from mid-October onwards, the plant should be given some rest for six to eight weeks and covered with a cardboard box so that it does not get more than eleven hours of light. This way, the poinsettia will once again wear its colourful leafy dress on time for Christmas.

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