The Christmas Cactus

I’d like to introduce you today to a plant that usually flowers at this time of the year, thereby being called often the Christmas cactus. Scientifically, it is called Schlumbergera, a small species of cacti with six to nine species found in the coastal mountains of south-eastern Brazil. These plants grow on trees or rocks in habitats that are generally shady with high humidity, and can be quite different in appearance from their desert-dwelling cousins. Most species of Schlumbergera have stems which resemble leaf-like pads joined one to the other and flowers which appear from areoles at the joints and tips of the stems. In Brazil, the genus is referred to as Flor de Maio (May flower), reflecting the period in which they flower in the Southern Hemisphere. Most of the popular houseplants grow with flowers in white, pink, yellow, orange, red or purple. The plants are offered for sale under a variety of common names. The earliest English common name was "Christmas cactus". In Europe, where plants are largely produced for sale in the period before Christmas, this remains the most widely used common name in many languages (e.g. Weihnachtskaktus in German, cactus de Noël in French, and cacto de Navidad in Spanish). This is also the name used in Canada. In the United States, where plants are produced for the Thanksgiving holiday in November, the name "Thanksgiving cactus" is also used. 

It was named after Frédéric Schlumberger, who had a collection of cacti at his chateau near Rouen. It was originally discovered in 1837 and named Epiphyllum russellianum. The plants need some light, cooler temperatures and occasional watering. Too much light causes stems to take on a reddish colouration; however, very low light levels will prevent flowering. Day length is important in controlling flowering; continuous darkness for at least 12 hours is necessary to induce bud formation. A period of about 8 days with 16 hours of darkness at 16 °C (61 °F) has been shown to cause flower buds to form.