Our Christmas Cactus usually blooms around Thanksgiving. Sometimes the buds drop off before they’re open. Can you tell me what’s wrong? What kind of care do they need?
It’s common to call all of those exotic looking winter-blooming houseplants Christmas cactus, but there is more than one type. (Schlumbergera bridgesii) is the botanical name for Christmas cactus, and it usually does flower around Christmas. But there is also S. truncata, or Thanksgiving cactus, which normally blooms about a month earlier.
In general, any of those “holiday” cacti need bright light and a moderate amount of water. Barbara Pleasant, in her book The Complete Houseplant Survival Manual, suggests letting the soil dry out a little between waterings, and providing a dose of a balanced fertilizer about once a month in winter.
Christmas cacti are photoperiodic plants – that is, they respond to the change in proportions of light and dark, and begin to form buds at the onset of longer nights and shorter days in fall. Blooms open a few weeks later.
They can also be finicky about a change in conditions once they begin to bud – if you move them around, for instance. “Once plants begin blooming, they may drop their blossoms if exposed to any kind of stress,” says Barbara Pleasant in her book about houseplants.
More information and care tips from the Clemson University Cooperative Extension Home & Garden Information Center: the Schlumbergera is native to Brazil, and they grow as epiphytes in tree branches in shady rain forests. They enjoy being outdoors in summer, but bring them indoors when nighttime temperatures get down to 40 to 50 degrees – and certainly before frost. Place them in a cool, dark room, and bring them out into bright light when buds begin to develop.
Here’s how to tell the difference between Thanksgiving and Christmas cactus: Look at the stem segments. Thanksgiving cactus each have 2 to 4 sharp serrations along the margins. The margins of Christmas cactus are more rounded. One other distinguishing factor: When the flowers open, look at the pollen-bearing anthers. The anthers of Thanksgiving cactus are yellow; those on Christmas cactus are purplish-brown, according to the plant experts.