Holiday Cacti (2013)

By Joe Merkelbach (January 2013)

The plants that are called Thanksgiving, Christmas and Easter cacti are quite different from the plants most succulent collectors prize. Rather than striking sculptural shapes usually compact in form, the holiday cacti are prized for their brilliant and bountiful blooms.

For all of the period from late fall through early spring, these varieties – there are many hybrid types and cultivars – provide a show of many shades. The cultivar color range goes from white and yellow through pink and peach to orange, fuchsia and finally bright red.

All of these plants are members of the tribe Rhipsalideae. There are six currently recognized species within the genus Schlumbergera, including the varieties identified as both Thanksgiving and Christmas cacti.

The Thanksgiving, crab or claw cactus, identified with the species S. truncata, has pointed tips at the ends of the stem segments or cladodes. Their flowers are held horizontally to slightly upwards and are zygomorphic (irregular) with yellow pollen grains. The cultivars with pointed-tipped cladodes and irregular flowers are termed members of the truncata group.

The Christmas cactus is identified with S. russelliana and has pendent regular (symmetrical) flowers with pink pollen grains. The ends of the stem pads are rounded rather than pointed in shape. These cultivars with rounded tips and regular flowers are members of the Buckleyi group. W. Buckley did the first crossing of species about 1852, and thus the Christmas cactus group was named for him.

One of my earliest memories of cacti is of my grandmother’s large (it had a semi-woody base stem), deep-orange Christmas cactus that bloomed faithfully for years.

The other four Schlumbergeras are kautskyi, microsphearica (with more cylindrical cladoes), opuntiodes and orssichiana. S. orissichiana is a source of recent “queen” cultivars.

The Easter cactus is currently assigned to the genus Hatiora with two species: the red-flowered gaertneri and pink-flowered rosea, as well as the cultivar Hatiora x graeseri, which has a range of colors.

The stems of these hatioras are very similar to those of S. russelliana, and they were formerly assigned to Schlumbergera. The flowers are sufficiently different that these species were moved to Hatiora by the current taxonomic authorities Barthlott and Nigel Taylor in 1995. The taxonomy of Rhipsalideae is tricky enough to induce a headache; you can follow it in the sources below or in Anderson.

All the species are native to the Atlantic rainforest of southern Brazil. This is a subtropical region with mountains very close to the ocean. The prevailing easterly winds blow humid ocean air against the heights, where cooler temperatures condense moisture into rain and fog.

The cacti are epiphytic or epilithic, usually living in minimal pockets of humus in tree crotches or rock cracks. Although there is plenty of rain in habitat, and the plants like high humidity, drainage is also very rapid, so the plants are not tolerant of standing water in cultivation. The cladodes root readily in damp sand, so it is relatively easy to get clones of desirable plants started.

The plants require cool weather and light exposure equivalent to shortening days in the fall to set buds, but will bloom year after year with attention to details. A good year-round application of fertilizer will increase the bud set number. Mature plants take quite a lot of space and are not all that attractive during most of the year, but during blooming season they are a great addition to happy holidays.

Sources:
Wikipedia – http://en.wikipedia.org/wiki/Schlumbergera
Wikipedia – http://en.wikipedia.org/wiki/Hatiora
Christmas Cactus (Schlumbergera) Care Guide – http://www.epicgardening.com/christmas-cactus/
The Cactus Family – Anderson, Edward F. – 2001