Schlumbergera (2019)

By Pat Mahon (November 2019)

As we approach the holidays, there is one cactus most notable for blooming this time of year. Most people simply call it the “Christmas cactus,” but this plant is more than just a throwaway companion to the poinsettia.

The plants sold in stores this time of year are actually Schlumbergera hybrids, coming in an array of colors. What most may not know is from where these cacti come. It is easy to assume they are simply tropical, but this is not entirely correct.

Schlumbergera is a rather small genus, consisting of up to nine recognized species. They are all restricted to the Atlantic coastal montane regions of southern Brazil, growing in higher elevations from 700 to 2,800 meters. The plants are either epiphytic or lithophytic, with photosynthetic stems and woody bases.

What is interesting is that the entire genus has adapted to being pollinated by hummingbirds. Flowers are colorful and tubular, and supply nectar to the pollinators. Most species require pollination from unrelated plants. We see an exception to this with species that occur at the highest elevations, where hummingbirds may be absent. These plants are receptive of their own pollen.

Fruits remain intact, as seed dispersal seems to depend on birds. Even more remarkable, these cacti may experience overnight temperatures dipping below freezing!

Today’s commonly available Schlumbergera are hybrids of S. russelliana, S. truncata and the hybrid S. x buckleyi (which is S. russelliana x S. truncata). The original introduction into cultivation began in the first half of the 19th century, and a resurgence of popularity began again in the 1950s.

Cultural Requirements

If you are just adding a schlumbergera to your collection, chances are that if you give it partial neglect in a shady spot, it will live and thrive enough to eventually share cuttings with friends and family.

These plants like an acidic, organic-rich soil, but it should be free-draining. So a peat-based grower’s mix and some lava rock, sand or similar media should be added. Watering should keep the plants consistently damp year-round, as too much or too little water can prove damaging.

Lighting is one of the most important aspects of this genus. Too much light can cause sunburn, while too little light may not be enough to initiate blooming. To initiate flowering, there must be uninterrupted darkness of 12 hours in a day for an extended amount of time.

If you can control lighting and temperature parameters, 16 hours of uninterrupted darkness a day for eight days at 61 degrees F degrees will initiate blooming. It is noted that during this time, falling to lower temperatures can slow down the bud initiation, and water should not be withheld.

So this winter, let’s not throw away our Christmas cacti … but what you do with Euphorbia pulcherrima is not of my concern!

Sources:
Wikipedia – https://en.wikipedia.org/wiki/Schlumbergera#cite_note-MHaIII-20
House Plant Expert – https://www.houseplantsexpert.com/christmas-cactus.html
International Plant Names Index – https://www.ipni.org/?q=schlumbergera