Schlumbergera truncata comes from the hills and mountains around Rio de Janeiro, in the Atlantic temperate rainforest area of Brazil. It commonly grows as an epiphyte, rooted in moss and debris in clefts of the tree trunks; or on rocks, in damp and shady conditions. It grows as a series of flat, leaf-like branching stem segments, initially upright or spreading, later hanging. Flowers appear as the days get shorter, and colder: in May in habitat (in the southern hemisphere), but around October or November in the UK. In wild plants the flowers are around 7cm long, in shades of pink, magenta, or orange, and are held more or less horizontally. Modern breeding has produced cultivars with more upright flowers, and additional colour forms, including whites and yellows.
Successful cultivation requires very different conditions to those for most other cacti and succulents. The plant needs an open organic based compost, diffuse light or dappled shade, and preferably higher humidity. It is often grown under the staging in a greenhouse (and forgotten about, for most of the year!) but can also be grown as a houseplant.
S. truncata will grow, and flower, perfectly well in winter temperatures down almost to freezing. To obtain the best colours on the paler forms, though, the plants need to be kept warmer – above 13C or so.
To propagate a particular variety, twist (or cut) sections of stem of 2 – 3 segments and treat these as cuttings. Roots develop around the base of each segment. Putting the cuttings in a plastic bag can help to keep the humidity high, without overwatering, until the roots are sufficiently developed. New plants can also be grown from seed, though the resulting plants can be very variable.
The common English name for this plant is said to be the Crab Cactus – presumably from a fancied resemblance of the arching stems to a crab, with toothed claws. But this name is rarely if ever used. Instead, many people refer to the plant, incorrectly, as the Christmas Cactus. That name however belongs to a hybrid between S. truncata and another species, S. russelliana, which flowers later. The real Christmas Cactus is less commonly seen nowadays, but is vigorous and reliable, and is also well worth growing.
Mark Preston
Copyright 2012 No part of this article or the accompanying pictures may be reproduced without permission
