Schlumbergera

Schlumbergera is a small genus 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 of the popular houseplants are cultivars of Schlumbergera, rather than species, with flowers in white, pink, yellow, orange, red or purple.

In most species the segments are strongly flattened (cladodes), being made up of a central core with two (or more rarely three) "wings".

Special structures characteristic of cacti, called "areoles", then occur at the ends of the segments of the stem.

The outer tepals – those closer to the base of the flower – are short and unconnected, and spread out or curve backwards.

The inner tepals – those towards the tip of the flower – are longer and in most species become progressively more fused together at the base to form a floral tube.

Lemaire placed only one species in his new genus – a plant discovered in Brazil in 1837 which had been named Epiphyllum russellianum by William J. Hooker.

[4] In 1913, Nathaniel Britton and Joseph Rose followed Lemaire in keeping Schlumbergera russelliana and Zygocactus truncatus in separate genera.

Following Ludwig Pfeiffer in 1837, the European tradition was to use Phyllocactus for epiphytic cacti with large regular flowers and Epiphyllum for the irregular-flowered species now called Schlumbergera truncata.

[17] Schlumbergera occurs only in the coastal mountains of south-east Brazil, in the states of São Paulo, Rio de Janeiro, Minas Gerais and Espírito Santo.

The natural distribution of Schlumbergera species has become confused because European cultivars were deliberately introduced into some areas, including the Serra dos Órgãos National Park, by the Brazilian Agricultural Department, to compensate for over-collecting of wild plants.

David Hunt describes collecting specimens in conditions of cloud, drizzle and overnight temperatures down to −4 °C (25 °F).

[21] Plants are epiphytic or lithophytic, growing on moss-covered tree branches or in rock crevices, often in small pockets of substrate formed from decayed leaves and other vegetation.

The exceptions are S. kautskyi and S. microsphaerica; as noted above, the latter is found at higher altitudes where hummingbirds may be absent or less common.

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 houses, 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.

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).

A difficulty is that the flowers of many cultivars exhibit different colours depending on the temperature during bud formation and growth.

[26] In the United States, cultivars are propagated in large numbers for sale before Thanksgiving Day (the fourth Thursday in November).

A single Dutch grower (de Vries of Aalsmeer, the Netherlands) was reported in 1989 as producing 2,000,000 plants per year.

Their specific recommendations include:[34] 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).

Flower cut in half vertically with the base to the left; the bases of the tepals form a kind of tube, the upper parts bending away from the tube; the stamens run the full length of the flower from left to right and emerge from the end; some start at the very base of the flower, others start from further along to the right, being joined to a tepal.
Zygomorphic flower, probably of a cultivar in the S. Truncata Group, cut in half to show its internal structure
Drawing is probably of a pressed specimen as it appears flat; the base is at the bottom and the plant then branches repeatedly – about six times in the longest branch. Most branches end in either buds or regular flowers which are pinkish.
Drawing of S. russelliana , the type species , from the Botanical Magazine, 1839
Map shows the coastline of south-east Brazil. A strip running roughly south-west to north-east along part of this coastline is coloured red. The red strip is about five times as long as wide and extends either side of Rio de Janeiro.
The distribution of most Schlumbergera species is discontinuous within the red area. [ 18 ]
A small portion of green stem is to the left. A yellow flower seen from the side extends to the right. Stamens and a style extend out of the flower. Running from left to right the flower tilts upwards. At the end of the flower the upper petals are only bent back a short way, whereas the lower petals are bent almost back on themselves.
S. Truncata Group 'Gold Charm'; note the very pointed teeth at the end of the segments, zygomorphic flowers held above the horizontal, and yellow pollen.
The picture shows a flower from more or less below. The tepals radiate outwards from the centre, more or less symmetrically. The petals nearest the viewer bend outwards less than those further away.
Member of the S. Buckleyi Group, viewed from below; rounded rather than pointed edges of the segments, pendant more or less regular flowers and pink pollen.