By Russell T. Nagata
University of Hawaii at Manoa
College of Tropical Agriculture and Human Resources
Komohana Research and Extension Center-Hilo
The Christmas cactus, Schlumbergera x buckleyi — a hybrid between S. russelliana and S. truncata and sometimes listed as Schlumbergera bridgesii — is a common holiday plant frequently seen at this time of year in full bloom. It is a native of the coastal mountain forest of southern Brazil, where it grows as an epiphyte on forest trees or moss covered rocks.
This native environment is generally relatively cool, shaded by clouds or forest canopy and of high humidity. And although not the environmental parameters we associate with cactus, these are true cactus. Like many cacti, the Christmas cactus has no typical leaves and the green that you see are actually flatten stems. Collectively, these cacti belong to a group of cactus known as stem cactus.
As with all cacti, the stem cactus has areoles located on the distal end of each stem section. Areoles are special structures that resemble tiny pin cushions of wool and bristles and are the location where flowers arise. In its native habitat, the Christmas cactus flower generally are a red hue, tubular shaped flower, and having abundant nectar, all characteristics that favor pollination by hummingbirds. Fruit and seed set require cross pollination and a reason that we have little or no fruit set here in Hawaii.
Modern-day plant breeders have developed a wider range of flower color from white, yellow, pink, red, and purple. As is the nature of gardeners, we love plant challenges and getting your Christmas cactus to re-bloom the following Christmas is a challenge not to be passed up. Once the flowers have died away the first decision may be to repot your cactus into a larger pot or into a more natural setting. When selecting a potting medium, choose one that drains well.
You can purchase a commercially available succulent media or mix your own using perlite or cinders and mixing with coarse peat moss or coir. Christmas cactus is also known to do well on tree fern trunk. Fertilize with a blooming plant fertilizer according to label directions. In outdoor locations, place plants in a semi-shady spot as to much light intensity may cause the development of red pigment in the stems or sunburn. When grown indoors, place in a well lighted location for good flowering.
Christmas cactus will grow under low light, but may not flower. Although it is a true cactus, the Christmas cactus does not thrive in extremely hot or dry environments. As previously mentioned, it thrives in a moist, cool, tropical environment and is one of the reasons it does well in Hilo. Propagation of Christmas cactus is easy to accomplish by planting stem segments.
After the bloom period, is a good time to prune your Christmas cactus to give you a bushier plant and to provide you with many cuttings that can be use for propagation. It is best to use two to four segment section of stem, placing each cutting in moist potting medium to a depth of one segment. Keep cuttings in a cool shady location for 3 week or until roots start to develop. During this period keep soil moist but not to wet. Excessive moisture will lead to conditions that can promote rot. Once roots are developed plants can be moved to a sunnier location. Flowering in the Christmas cactus can be initiated by two environmental triggers, day length or cool temperatures. When days are shorter than 12 hours, bud formation is initiated and your plant should be blooming in 6 to 8 weeks. Avoid house or street lights to insure good blossom production in the Christmas cactus and keep them away from excessive heat sources. Another reason why your plants have not bloomed or bloomed off season is that it is not a Christmas cactus. During the fall we see blooming stem cactus and generally give it the common name, Christmas cactus.
However, what you bought or received might be the Thanksgiving cactus, Schlumbergera truncata, or the Easter cactus, Rhipsalidopsis gaetneri which looks very similar to the Christmas cactus. The Christmas cactus has a scalloped stem section with no points and flowers are borne on the tip section and are pendent. Also, the branches are arcing and pendent in appearance. Natural blooming period is during November and December in the northern Hemisphere, but may also bloom a second time between March and May. Thanksgiving cactus has 2-4 pointed teeth along the stem edge. Flowers protrude horizontally from stem tip. The Easter cactus has rounded teeth along the stem edge, tiny bristles on the tip of the end segment and typically blooms only once in the spring. This plant species also has the characteristic of shedding its stem sections when water stressed as in drought conditions. Whichever stem cactus you have growing, with the proper care it will give you years of beautiful blossoms and unlimited opportunities to share this wonder plant. For more information on this and other gardening topics, please visit the CTAHR electronic publication website at http://www.ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices around the Island. I can be reached at firstname.lastname@example.org.