Many of us will know Euphorbia pulcherrima as poinsettia but other common names, such as Mexican flame leaf or painted leaf, are also used. Joel Roberts Poinsett was the first Ambassador from the USA to Mexico in 1825. While he was there he sent some plants of Euphorbia pulcherrima back home to South Carolina where the plants were grown in spite of their relatively short flowering period. The name poinsettia was given to the plants, honouring the man who introduced them to cultivation.
Euphorbia is a large genus of plants, many of which are succulent, however, Euphorbia pulcherrima is a non-succulent, evergreen, winter-flowering shrub. In its native Mexico, it grows to about three metres tall, on the edge of forests, flowering in December. Typical of the genus, it has small, yellow flowers, but it is the bright-red, leaf-like bracts surrounding the flowers, that catch the eye.
Wild Euphorbia pulcherrima is a leggy plant, reluctant to branch, and produces relatively small bracts compared to the plants that we see today in cultivation. Thus, it largely remained until the 1960s when work was carried out to produce short, branched cultivars. In addition, chemicals are used to keep the plants at the more manageable 30-60 cm tall for pot cultivation. Cultivars are available with bracts of red, pink, cream, white, doubles and marbled and some novelties may be only a few centimetres high.
The other important fact to know about growing Euphorbia pulcherrima, is that it is a short-day plant. This means that it needs around 14 hours of darkness, with no artificial light, from October to late November. At this point, the dark treatment can be stopped and the flowers should develop and the bracts colour up. It is possible to do this at home, but the plant is liable to be taller, not having been treated with chemicals to reduce the height and also it should be cut back in spring to produce new growths. Poinsettias particularly dislike cold draughts and should not be kept by a window, nor should they be overwatered as this can cause wilting and leaf drop, as can under watering and lack of light.
Euphorbia pulcherrima has been used in its native homeland to decorate churches and the Aztecs used the leaves to dye clothing and the milky sap for medicinal purposes. Of course, today it is important commercially as a pot plant at Christmas time.
Albrecht Llamas K 2003. Tropical flowering plants. A guide to identification and cultivation. Timber Press.
Phillips R and Rix M 1998. Conservatory and indoor plants, vol 1. Pan Macmillan.