History Schlumbergera truncata was in cultivation in Europe by 1818, and
S. russelliana was introduced in 1839. The two species were deliberately crossed in England by W. Buckley, resulting in the
hybrid now called
S. ×
buckleyi, first recorded in 1852. By the 1860s, a substantial number of
cultivars (cultivated varieties) were available in a range of colours and habits, and were used as ornamental plants in "stoves" (heated
greenhouses) and in homes, where they were popular for their autumn and winter flowering. Many cultivars were selected seedlings of
S. truncata, but at least three
S. ×
buckleyi hybrids were available, of which one, now called
S. 'Buckleyi', is thought to be the original Christmas cactus. By the early part of the 20th century, the genus had become less popular, and many of the early cultivars were lost. From around the 1950s onwards, breeding resumed in Europe, North America, Australia and New Zealand. New plants were produced by crossing among the species and existing cultivars of
S. truncata,
S. russelliana and the hybrid
S. ×
buckleyi. Treatments which induced
mutations were also used. The result was a wide range of flower colours which had not been available before, including the first true yellow to be sold commercially,
S. 'Gold Charm' (which was a sterile
triploid). Breeders aimed for plants which grew strongly, were upright at the point of sale rather than pendulous, had many flowers or buds, and were adapted to living as houseplants. The Easter cactus or Whitsun cactus was placed in the genus
Rhipsalidopsis , but was at one time included in
Schlumbergera (or one of its synonyms). The name "holiday cactus" has been used to include both
Schlumbergera and
Rhipsalidopsis cultivars. •
Growing medium: Free-draining,
humus-rich, somewhat acid growing media are used for commercial production, such as a mixture of
peat or
leafmould and an inert material such as grit, sharp sand or polystyrene beads. It is recommended that plants should be grown in relatively small pots; half-height pots are suitable. •
Watering: They are more tolerant of drought than many house plants, though not as drought tolerant as the desert cactus. They can be damaged by both under- and over-watering. Keeping the growing medium just moist throughout the year avoids either extreme. •
Light: They can be damaged by exposure to more than small amounts of sunlight. Members of the Buckleyi Group, such as the old-fashioned Christmas cactus with pendant flowers, are more tolerant of high light levels than members of the Truncata Group, such as most of the modern cultivars. 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 has been shown to cause flower buds to form. Lower temperatures slow this process. The advice sometimes given to withhold water to produce flower buds has been shown to be incorrect. • Temperature: Holiday cacti grow best when they are placed in a location with partial shade, with a temperature between . They can not tolerate temperature less than 10 °C (50 °F). •
Propagation: Both commercially and in the home, propagation can be achieved by using short pieces of stem, one to three segments long, twisted off rather than cut. Cuttings are allowed to dry for 1–7 days, forming a
callus at the broken end, and then rooted in an open growing medium. Temperatures above and up to in long day/short night conditions speed rooting. File:Schlumbergera IP.jpg|alt=A plant with green upright stems is growing in a blue pot. There are a few flowers and buds at the end of the stems, all more or less upright.|Young plant of a member of the
S. Truncata Group; still upright and therefore more convenient for selling File:Schlumbergera growth.jpg|
Schlumbergera new growth. The upper view shows bright red new cladodes forming, the centre shows maturing growth, the lower view shows two
aerial roots extending down
Pests and diseases In cultivation, these plants have been described as "remarkably free from pests and diseases". Two significant insect pests are
aphids on young shoots, buds and flowers, and root
mealybugs which attack below soil level. Stems and roots can be rotted by diseases caused by fungi and similar organisms; these include infections by species of
Fusarium (a
fungus), and
Phytophthora and
Pythium (both
water moulds). Approved chemical treatments can be used in the case of insect attack or these diseases. Aphids, mealybugs and other invertebrate pests can spread
viruses. Symptoms vary with the species, but a loss of vigour is usual.
Cactus virus X has been isolated from
S. truncata. There is no treatment for virus diseases; it is recommended that infected plants be destroyed. ==References==