A popular gift plant, the Christmas cactus needs darkness to bloom

November 25, 2020

It probably isn't one of life's more pleasant moments to be called before the Roman Inquisition. In 1616, the Inquisition warned Galileo not to take up heliocentrism, the belief that the sun is the center of our solar system. The church taught that the earth was the center of the universe. But now, the shorter days of fall and winter play games with us. From where we stand, the sun marches across the sky every day, when, of course, we’re the ones spinning around the sun at 67,000 miles per hour. As if that isn't enough, we also spin 1,000 miles per hour around on an imaginary line called an axis. But it is the tilt of the earth on that axis that gives us summer when it tilts toward the sun, and now winter as it tilts away from the sun.

Plants, like people, need darkness to thrive. There are plants that actually need at least 12 hours of darkness in order to bloom. They include Kalanchoe (Kalanchoe spp.) and Salvia (Salvia spp.) along with vegetables such as green onions (Allium cepa L.), Texas early white onions, Bermuda onions and soybeans (Glycine max), and the short-day strawberries Allstar, Annapolis, Camarosa, Cavendish and Earliglow.

A popular gift plant, the Christmas cactus (hybrid Schlumbergera × buckleyi), needs darkness to bloom. A quick way to see if you have a Christmas or Easter cactus, or a Thanksgiving kind, is that Christmas and Easter cacti have slightly rounded leaves and Thanksgiving cacti have pointy leaves.

Christmas cactus plants need dark, cool treatment for about six to eight weeks to set buds. Once the flower buds have formed, the blooms open up in 12 weeks or less. Move your Christmas cactus plant when ready to bloom to a bright, sunny, spot away from drafts. Be careful it isn't in hot, direct sunlight, because this may cause the plant to droop. Likewise, a harsh draft can shock the Christmas cactus and cause the buds to drop.

To have even more blooms next year, you can feed your Christmas cactus every month during the growing season, usually from April through October. This feeding stores energy to produce next year's flowers. Christmas cactus also produce far more blooms when they are slightly potbound.

All succulents and cacti grow best in dry environments and need their soil to dry out completely in between watering. The best soil for Christmas cacti is made up of light, airy materials with excellent drainage. Choose specially mixed cactus potting soil or lighten regular potting soil by adding sand or pumice.

Because indoor air is notoriously low humidity during the fall and winter, try misting Christmas cactus regularly with water. If the buds fall off just before they open, you may be overwatering. Just cut back on watering and misting. Remember that Christmas cacti, like all succulents, need significantly less water during the winter when they are dormant.

Christmas cactus are ridiculously easy to propagate. Just cut off a piece of the stem and stick it into a small pot filled with cactus potting soil. Within two weeks, the cutting will form roots. Enough to give away as gifts – or bribes, if the Inquisition comes calling.

  • Paul Barbano writes about gardening from his home in Rehoboth Beach. Contact him by writing to P. O. Box 213, Lewes, DE 19958.

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