Why won’t my Christmas Cactus bloom?

Published 7:44 pm Thursday, December 8, 2022

The Christmas cactus is a traditional and very festive gift this time of year. We browse by them in grocery stores, flower shops and many other establishments throughout the holiday season. They have beautiful blooms of white, pink, red, to peach. They make wonderful houseplants but, like many plants that we receive as presents, they require a little care after purchase to keep and encourage return blooming.

There are a couple of things to understand before we can talk about re-bloom in Christmas cacti. First, not all of these plants are Christmas Cacti. Often, we are purchasing a Thanksgiving Cactus (Schlumbergera truncata) not a Christmas cactus (Schlumbergera bridgesii). The differences between the two are very subtle but make all the difference in blooming.

The Thanksgiving cactus is an earlier bloomer by approximately a month (typically around Thanksgiving), making it a better seller for the Christmas season. One of the easiest ways to distinguish between the two plants is to look at the shape of the flattened stem segments called phylloclades. The Thanksgiving cactus has two to four points or teeth along the margins. Conversely, the Christmas cactus has a lobed or rounded margin. Another way to tell the difference is during bloom. The Thanksgiving cactus has yellow anthers (pollen bearing structures) and the Christmas cactus will have purple to brown anthers.

So, how do we get them to bloom? I went on a trip in September and so my office stayed closed up and fairly cold from our air-conditioning. I would guess that it was in the high 50’s for the better part of the entire week. Approximately two weeks after I returned, my Christmas cactus was in full bloom. We can use temperature to force blooms on both the Christmas and Thanksgiving cactus. Keep night time temperatures between 50°F and 59°F until buds are set. Do not let them get below 50°F or injury may occur. After bud set, keep them between 60°F and 68°F, preferably closer to 68°.  Photoperiod can be manipulated to force bud set as well. Continuous darkness for 13-14 hours each night for approximately six weeks will force bud set. Both methods have their limitations. As little as two hours of light interruptions could inhibit bud set. If you are using temperature, plants will be injured at temperatures lower than 50°F. Temperature forces bloom regardless of photoperiod. The fool-proof method is using both together.

Propagate between May and June to give these as gifts to your neighbors next Christmas. If you have one or several, they are very easy to propagate to use as gifts for the next season. Simply count three to four phylloclades back from the terminal end of the stem and pinch it off at the joint. Allow to sit out in a fairly dark room for 24-48 hours. This allows a callus to form where you pinched it apart from the main plant. This callus helps to stimulate root growth and to protect against rot while roots are forming. Once the callus has formed, plant the callus end of the segment ½” to 1” deep in a clean, moist, potting soil. Place the container in bright, indirect sunlight. Roots will form in three to eight weeks and the plant will begin to grow new segments. Once the new growth begins you can transplant into a larger pot. Propagating several at one time will ensure better success.

If you have a question to submit, please email to me at gene_fox@ncsu.edu. Having trouble with growing in your home landscape, ask an Extension Master GardenerSM Volunteer (EMGV’s) through the Blacklands Area Horticulture Facebook page or visit the Extension Office located at 155 Airport Road in Washington, NC.