Schlumbergera questionsby Dick Kohlschrieber
Reprinted from The Epi-Gram, Newsletter of the South Bay Epiphyllum Society
I had several people ask me how the commercial growers regulate when Schlumbergera are going to bloom. One of our members said she had been told by a nurseryman that you had to put your plant in a closet if you wanted it to bloom. That advice always makes me mad because it almost sounds cruel to do that to a plant. And it doesn't make that much difference in whether or not a plant will bloom. I have done this and came to the conclusion that most of these plants will bloom when they're going to bloom.
I also had been told to withhold water from the plant for a month and that would stress the plant enough to make it bloom. This is not true and has been proven to be harmful to the plant.
It happens that Schlumbergera are “thermo-photoperiodic''. This means that their bloom initiation is triggered by a combination of day length and temperature. The primary trigger is the day length. Once the day length decreases to approximately twelve hours, the plant recognizes that it is time to bloom. Night temperature of 55 to 65 degree F. should accompany the short day.
Schlumbergera are very sensitive to light and plants that sit in the house and are exposed to any kind of light in the house, may not form buds. I have even heard of plants that are affected by a street light outside. I suppose that this is where the idea of putting your plant in a closet came from.
I have mentioned before how sensitive Schlumbergera are to temperatures. If nighttime temperatures go below 50–55 degrees, pinking occurs in the white, yellow and pastel flowers. That's why the warm temperatures we had the third week of November have affected the colors of my flowers and I've had less pinking than I've had in years. I have also found that plants that have flowers that have a lot of pink will lose most of the pink coloration if the plant is put in a warm area.
Growth regulators and other chemicals have been used to assist bud formation and bud drop and I'm sure that many of the commercial growers use them. It has been shown that spraying with benzylaminoprine (BA) increased the number of buds per segment. Silver thiosulphate has been shown to be effective in reducing bud drop.
Most of the people that I know that grow a lot of Schlumbergera do not do a lot of fertilizing. I never have fertilized my plants as much as I did my epies and they seem to grow well and bloom a lot.
But when I have used a water-soluble fertilizer, the plants seemed to respond in a short period of time. Cobia, in his book Zygocactus (Schlumbergera)-A Comprehensive and Practical Guide For the Weekend Gardener, recommends using a 20–20–20 fertilizer 2–4 times a year. He also recommends leaching the plants with plain water to regular intervals to prevent the buildup of soluble salts. Fertilizer applications should stop at least one month prior to bud set.
McMillan and Horobin, in their book Christmas Cacti—The Genus Schlumbergera and its Hybrids, also recommend using a diluted well-balanced fertilizer and they also recommend leaching the plants with plain water.
They also say that fresh mulches of organic matter such as peat or leafmold, or even old tea leaves, placed around the plant on the soil surface can be beneficial and can keep a plant going for several years without repotting. They repeat a story that they published in an early issue of EPIPHYTES that I always liked. It was about a Christmas cactus, owned by an elderly woman, 4 feet in diameter in a 7-inch pot, in fine condition and full of bloom. It had been repotted 32 years previously and over the years was watered with tea and mulched with tea leaves.
REPOTTING-I have learned the hard way that you shouldn't be in a hurry to repot your Schlumbergera plants. The plants seem to do best when they are tightly potted. If you have a plant in a four-inch pot and want to repot it, I'd put it in a five-inch pot. It's also a good idea to use a pot that isn't too deep.
PRUNING-I have always pruned my plants right after they quit blooming. The experts recommend waiting until Spring and it may be that if you want to start new plants from your cuttings that result from pruning, they might root quicker in the Spring. Some of the experts recommend taking off at least 2 segments from each branch. I usually take off enough segments to even out the plant all around. On many of the Cobia hybrids it's essential to do some pruning or you'll just have these long unattractive stems. By the way, it's better to twist off the segments rather than cut them.
After the plants quit blooming, they very often look terrible. Some of my plants that bloomed early, look wilted. Wilting in Schlumbegera does not mean that the plant needs water but more often it means that the roots have rotted or that it's stressed in some way. Always pull on the wilted plants and if the roots have rotted, the plant may pull out of the pot easily. If the roots haven't rotted, put the plant in a shady area and cut back on the water.
I have quoted a lot from McMillan and Horobin's book and also Mark Cobia's book. Christmas Cacti—The Genus Schlumbergera And Its Hybrids by A. J. S. McMillan and J. F. Horobin is still available through Rainbow Gardens Bookstore. It is a wonderful reference book filled with color pictures and a list of all of the hybrids, including the Australian ones that were known at the time of publication.