By Katie Drewitz
University of Minnesota
Is your Thanksgiving cactus blooming? Has your Christmas cactus set buds? There are several factors that are required for the tropical plants of the Schlumbergera family to bloom.
The Thanksgiving and Christmas cacti received their name because the typical bloom period is near to the holiday, however, that is not always true. Bloom periods are triggered by the amount of daylight and the temperature. Therefore, your Thanksgiving cacti might be in bloom at Halloween and your Christmas may bloom closer to Thanksgiving. A more definitive way to tell the difference between a Thanksgiving cactus and a Christmas cactus is by looking at the segments of the leaves. The Thanksgiving cactus’s leaf segments have a pointed, jagged edge, while the Christmas cactus’s leaf segments are smooth and rounded. Another way is to look closely at the flower parts of the plant. The anther, pollen bearing part of the flower, is yellow on the Thanksgiving cactus and purplish brown on the Christmas cactus. Very often the Thanksgiving cactus is sold under the name Christmas cactus, which only adds to the confusion.
To initiate flowering the plant needs less than 12 hours of light per day and temperatures of less than 68°F. Flower buds will set regardless of the daylight hours if temperatures are less than 55°F. If the conditions in your home do not meet these requirements, extra efforts need to be done by the plant owner to trigger the cactus to bloom. Simply cover the cactus or put it in a dark closet for at least 12 hours a day. A room that is not used on a regular basis could also work well. In some warm homes, if temperatures never drop below 70°F, the plant may never bloom regardless of the amount of light.
Be aware that if budded plants are brought into a warm room with low humidity, they may drop their buds. Also, plants that are overwatered may even drop their leaf segments. The perfect place for the cactus is in a bright, indirectly lit room with suitable temperatures away from drafts. Water the plant when the growing medium is dry to the touch. Do not overwater and let the soil to be waterlogged, especially in the winter. The soil medium should be kept evenly moist in the fall when flower buds are set, to prevent them from withering. Never let water stand in the saucer below the pot. Fertilize the plant with a general-purpose fertilizer monthly during the growing season, fertilize with half strength from late winter through summer, and finally, stop fertilizing in late summer for greater flower bud production.
After the cactus is done blooming, they benefit from a “resting” period. Allow the soil to dry out between watering, but do not allow the leaves to shrivel. Thanksgiving and Christmas cacti bloom best when slightly pot bound. The best time to repot is in spring when new growth begins. The best potting medium is well-drained with good aerations, such as a mix of two-thirds potting soil with one-third perlite or coarse sand. Do not use a cactus soil mixture.
Take a close look at your holiday cactus, is it a true Christmas cactus or is it a Thanksgiving cactus? Regardless, with the proper care this plant will bloom for six to eight weeks each year for many, many years. For more information on all houseplants visit www.extension.umn.edu/garden/yard-garden/houseplants. If you have questions about this or any other agriculture, horticulture or natural resources question please reach out to your local Extension educator. Residents in Fillmore and Houston counties can call (507) 765-3896 or (507) 725-5807 or email email@example.com.