Zygocactus truncates: Christmas Cactus
The Christmas cactus needs no introduction for it is one of the most widely cultivated of plants. It is native to the mountains of the State of Rio de Janeiro in Brazil, where it grows as an epiphyte on trees and shrubs or as a petrophyte on stones, but always in the partial shade of tall trees. For this reason even in cultivation, unlike other cacti, it does not tolerate full sun.
Rising from the short woody stem are richly branched shoots composed of flat, leaf-like joints. These are of widely diverse shape – in the type species there are 2 to 4 teeth on the narrower edge of each joint. Nowadays, forms with very sharp, pronounced, large teeth as well as ones with smooth-edged joints are cultivated. Theare zygomorphic, 6 to 8 cm (2-1/4 to 3 in) long, and pinkish red in the type species; in cultivars the colour ranges from white through salmon to violet red.
Though it may be grown as an epiphyte, Christmas cactus cultivars do better in athat is sandy and light but at the same time rich. John Innes potting compost No. 1 with extra sharp sand added would be suitable.
Growers often complain that the plants do not flower. Usually the reason is that they do not provide them with the two rest periods that zygocacti require. One is approximately a three-month period from August till October (or November) and the second is after flowering has finished, in February to March. At both these times the temperature should be lowered (in the autumn by placing the plant in the window) and watering reduced to the minimum. The joints produced during the current year will thus ‘ripen’; then in late November, when the buds are visible, the plant should be moved to a warmer spot and watering resumed, also syringing. After flowering the temperature should again be reduced and water withheld altogether.
Christmas cactus may be propagated readily by detaching the joints, which will quickly form roots in moist sand.