Christmas cactus (Schlumbergera) make great holiday plants because they're easy growers and reliable bloomers. With a little extra care they will also bloom around Easter time.
Even though they're called cactus, these plants are different from common desert cactus. Rather than growing in the desert, they grow in the same "tropical" conditions most orchids grow in. Since they're "tropical cacti", their cultural requirements are different from true cacti.
Light: Christmas cactus require bright light with some direct sun. If you're growing outdoors in the summer, avoid direct sun and put plants in total shade.
Water: These plants enjoy thorough waterings with a dry period in between. That's easy with hydroponics! Simply water to 1/2 on gauge and then wait a week or so AFTER THE WATER GAUGE READS EMPTY before rewatering (or lift inner pot to check for dryness before rewatering).
Nutrients: In nature these plants get by on slim diet of bird droppings, decaying leaves, and anything else that comes their way. Apply a low dose of fertilizer (1/2 recommended strength) on a regulars basis. We use (and recommend) Dyna-Gro Grow 9-7-5 formula at 1/4 tsp per gallon.
Applying a "Bloom" fertilizer WILL NOT make your plant bloom. These plants have internal calendars that tell them when to bloom. Flowering is triggered by temperatures in the 50 degree range in the fall.
Temperature: These plants will grow in a wide range of temperatures without complaint We've grown good looking Christmas cactus in poorly vented greenhouses where temperatures reached 100 degrees or more during the and dropped below 50 degrees at night (the plant in the photos above are one of those plants!).
Christmas cactus like at least 40-50 percent humidity. If your house is dry during the winter, think about improving humidity levels now. A good way to increase humidity is with Humidity Trays.
Grower Tip: Christmas cactus have internal calendars that tell them when to bloom and you can't change it.
Temperatures: Starting in September or October, put your plant in a cool room where temperatures drop to around 50 degrees at night. (If you're growing outdoors, simply leave your plants outside until evening temperatures drop into the 50 degree range. Don't expose them to freezing temperatures however.)
This may not be as difficut as it sounds if you're growing indoors. When the weather turns cold outdoors, windowsills can be 10-15 degrees cooler than the rest of the room. (A Hi/Lo Thermomter is a good way to measure this.)
Light: Continue with bright light and some sun. Try to keep plants away from artificial lights in the evening because that can interfere with setting blooms. Commercial growers go to great lengths to keep plants totally dark for at least 12 hours to insure blooming.
Water: Start watering less. With hydroponics that means pouring water over the pebbles until the water gauge moves, then stop. Lift inner pot to make sure everything is totally dry before rewatering - usually about 2 weeks. Skip nutrients altogether during this period.
You should see blooms December - January.
Flowering lasts only a couple of weeks, but these plants can bloom several times a year. Blooms typically last only a couple of days before discoloring and falling off. To prolong life of flowers:
- provide extra humidity. Unlike desert cactus, these plants like 40-50 percent humidity. Use a Humidity Tray or some other method to provide extra humidity to increase the life of the blooms.
- lower temperatures. Just like any other flowers, Christas cactus blooms last longer in cool temps.
- never place in cold drafts, near heating ducts (or the fireplace) when blooming.
One of the most frustrating things is to see your Christmas cactus drop its buds before flowering. Bud drop is usually caused by 1) over-watering, 2) temperatures that are too warm, or 3) not enough light.
After the blooming season is over, give your plant a resting period of a month or so. Put it in a cool room and water it just enough to avoid dehydration. Simply wet the pebbles every week or so. Don't worry if your plant loses a few leaves and appears weak during this rest period.
After a month, start the new growing season by increasing water and nutrients. This is best time to convert to hydroponics.