A healthy plant in full bloom is a great gift for the special gardener on your holiday shopping list. While the poinsettia remains the most popular blooming plant for the holiday season, one of the most beautiful blooms to be found during the winter belongs to the Christmas (holiday) cactus. The true identity of the latter is a source of much confusion.
Christmas cactus (Schlumbergera bridgesii) is often mistaken for the Thanksgiving cactus (Schlumbergera truncata) because of their close proximity of their bloom dates. As a matter-offact, most of the Christmas cacti sold each year actually are Thanksgiving cacti mislabeled. To make matters even more confusing, many cultivars of Christmas cactus on the market today are hybrids between these to species. Perhaps it would be best that we refer to the two species and their hybrids collectively as ‘holiday cacti’. For the sake of those who want to know how the two species can be identified from one another, the Thanksgiving cactus bears leaf segments (phylloclades) that have serrated edges with 2-4 claw-like appendages. The true Christmas cactus has phylloclades with dentate margins.
Holiday cacti are native to a small region north of Rio de Janeiro, Brazil where they experience a “wet season” from December until March and a “dry season” for the remaining months. Holiday cacti are epiphytes in nature and often root into decaying debris trapped among tree branches or in rocky crevasses in shady areas on the ground. Although they are true cacti, they are tropical cacti and not quite as drought resistant as their name might imply. This is important to remember when considering the cultural requirements of this plant.
While holiday cacti can tolerate low light, they perform best in bright indirect light in the home. Brighter light is beneficial during the winter but full sun during the summer months can burn the plant and result in palelooking plants. If plants are moved outside during the summer, be sure to keep them in a shady or semi-shady location. The ideal temperature for holiday cacti is between 70 and 80 for it growing season which is from April to September in the northern hemisphere.
Proper watering is vital for success with holiday cacti. Like most cacti, holiday cacti will not tolerate “wet feet”. Holiday cacti are much more tolerant of under-watering than overwatering and should be watered only when the growing medium is dry to the touch. If a saucer is placed under the pot to collect drainage, but sure to empty it and not allow the excess to be wicked back in the pot over several days. Failure to do so will result in a soggy root environment which is an open invitation to root rot. Reduce watering from fall through spring and only fertilize plants during their growth period of early spring through late summer. When fertilizer is called for apply a regular fertilizer at one-quarter strength or a houseplant fertilizer according to label directions.
Holiday cacti should be kept slightly potbound to induce prolific flowering. When repotting becomes necessary (about every three years), the growing medium used should be very porous and well-drained. Commercially available peat-lite mixes formulated for epiphytes are good choices. Regular peat-lite mixes can be made into epiphytic mixes by incorporating additional amounts of perlite or sterile sharp sand to increase porosity.
Reblooming holiday cacti can be a bit challenging. Holiday cacti are short-day (long night) plants but the response to daylength is modified by temperature. Indeed, flowering will occur regardless of daylength under cool night conditions (50-55o F). Most prolific flowering occurs when plants are exposed to short days with at least 13 hours of darkness each night and cool night temperatures. Reducing the amount of water to slightly stress the plant at this time will also aid in the flowering process. Subjecting holiday cacti to short days, cool nights and dry conditions in mid-October will cause plants to be in full bloom for the holiday season.
Holiday cacti commonly drop unopened flower buds when suddenly stressed. This can be the result of a sudden change in temperature, light or other environmental factors such as excessive drying of the growing medium. Poor flowering is often due to stray light interrupting the required long, uninterrupted period of darkness during short-day treatment. Interior lights in the home, street lights or even car lights can disrupt the required dark period and cause disappointing flowering. Additionally, holiday cacti are very prone to root rot. This can be prevented by avoiding excess watering and maintain strict sanitation when culturing the plant. The most common insect pests include mealybug and scale which are most easily dealt with by physically removing them from the plant.
Given proper care, holiday cacti often outlive the caretaker and provide years of brilliant color around Christmas. The small amount of effort required by these plants is well worth it when one considers the reward of seeing an “heirloom” plant bloom year after year.
REVISED: August 1, 2012