A holiday cactus in full bloom is a great holiday gift. Easy to care for, holiday cacti generally are long lived and will easily bloom year after year. In fact, they are often passed down from generation to generation as family heirlooms.When selecting a new plant, look for sturdy, healthy green foliage and new flower buds. Avoid diseased or insect-damaged plants, said Jennifer Fishburn, a horticulture educator with University of Illinois Extension. Exposure at freezing temperatures even for a short time can damage leaves and cause flower drop, so before taking them outdoors, carefully wrap plants. As with all houseplants, avoid placing plants near register vents or in drafty areas.
"Holiday cacti include the Thanksgiving cactus, Christmas cactus, and Easter cactus," Fishburn said. "The holiday cacti are easily identified by the stem margins. These cacti don't have true leaves; instead they have flattened stem segments.
"The most widely grown species is the Thanksgiving cactus, also called a crab cactus,Schlumbergera truncata. The stem margins have two to four saw-toothed projections resembling crab claws. Flowers are produced from late November to late December. Thanksgiving cacti are often forced into bloom and sold at Christmas time, and are often misnamed Christmas cacti. Flower colors include white, red, lavender, salmon, orange, and yellow.
Christmas cactus,Schlumbergera x buckleyi, has scalloped or rounded stem margins. Flowers are generally showy from late December through March. The flowers are formed at the tip of the segments.Easter cactus,Rhipsalidopsis gaertneri, has four to six rounded teeth along the stem edges and brownish hairs at the leaf tips. Shades of pink or red flowers appear during March through May. Easter cactus may re-bloom.Thanksgiving and Christmas cacti blooms are triggered by day length. They bloom when they receive 12 to 15 hours of darkness each day for five to six weeks combined with cool night temperatures. Some cacti will bloom if exposed to prolonged cool temperatures between 50 to 55 degrees during the fall regardless of day length.
"To initiate flower buds, place Thanksgiving and Christmas cacti in a room that doesn't receive artificial light at night such as a spare bedroom or basement," Fishburn said. "Cacti can also be placed in an unheated porch until temperatures reach 45 degrees. Plants should receive bright light during the day with 55 to 65 degree temperatures.When plants are in flower, keep them in a bright, indirect light. Ideal temperatures are 70 degrees during the day and 65 degrees in the evening. "Don't let the soil dry out during flowering. Flower buds will drop if they receive too much light, are exposed to drafts or temperature extremes, or if the soil gets too dry," Fishburn pointed out.
"If plants fail to flower, this could be due to interrupted nights or high temperatures."During the growing season when the plant is not flowering, water plants thoroughly but let them dry slightly between waterings. A major disease of holiday cacti is root rot caused by overwatering. Water when the top inch of soil is dry to the touch. When the plant is actively growing, between April and October, fertilize every two to four weeks with a complete houseplant fertilizer, following the directions on the label. Holiday cacti require a bright but filtered light indoors. Keep in mind that holiday cacti thrive on neglect."This winter, brighten up the indoors with a flowering holiday cactus," Fishburn said.