Why isn't my Christmas Cactus blooming? This is a common question we hear from the community this time of year.
First things first, you need to identify the kind of cactus you have. There are 3 different types - Thanksgiving, Christmas and Easter.
As you can see in the picture above, the best way to tell them apart is by their leaves. The Thanksgiving cactus, or Schlumbergera truncata, is distinguished from a Christmas cactus by inspecting the leaves. The leaves of a Thanksgiving cactus are much pointier. In addition, each segment has serrated sides with pointed spines, which is likely why this plant is also known as “Crab Claw Cactus.”
A Christmas cactus, or Schlumbergera bridgesii, has a much softer look to its leaves, the segments have scalloped edges, and the ends almost look like they go straight across. To make it even more confusing, the heirloom Christmas cactus (Schlumbergera x buckleyi) that your grandparents probably had is seldom sold online or in stores. Fortunately, it is still preserved today by gardeners passing it on.
The Easter cactus leaves have rounded edges with star-shaped blooms. Christmas and Thanksgiving cactus flowers are more tubular and may produce a second smaller flush of flowers in spring, while the Easter cactus blooms only once per year.
Take time to inspect your plant’s leaves, and it can help you understand if it is a true Christmas cactus or not. One of the great things about a Christmas cactus is that it doesn’t shed leaves like poinsettias or other houseplants. Since there are no true leaves, photosynthesis occurs within the green stem segments known as phylloclades. Pinch back the stems in early June to promote branching terminals for more flowers, and use stem pieces with three to five segments to root new plants.
Now that you have figured out the type of cactus you have, you may be surprised to learn that the initiation of flower buds is dependent on the amount of daylight it receives. If the plant is kept indoors year-round, then their normal cycle of daylight exposure can be interrupted by artificial light inside the house.
The secret of good flower bud production during the fall involves temperature regulation and photoperiod (length of day and night) control. Fourteen hours or more of continuous darkness each night is required before flower bud set will occur.
Long nights should start around the middle of September and continue for at least six continuous weeks for complete bud set. Note that as little as two hours of interrupted lighting will inhibit flower bud set. Buds normally will be visible in about four weeks. The photoperiod has no effect on flowering once the buds are set.
Keep in mind that artificial lighting can easily break the cycle. Therefore, the best way to avoid this is by placing your Christmas cactus in a room that isn't used in the evening.
Flowering can last seven to eight weeks if the plants are kept at 68 degrees Fahrenheit. Christmas cactus tolerate dry, slightly underwatered conditions during the spring and summer. Do not let the soil become waterlogged, especially during the long nights of winter. Following bud set in the fall, the soil must be kept evenly moist to prevent flower buds from falling off. Never let water stand in the saucer beneath the pot. Follow these tips to enjoy your Christmas cactus for many years to come.