Friday, February 14, 2014

Growing a Happy Christmas Cactus -- Lessons from Junior

Christmas cactus flower
Christmas cactus flower
I've been growing a plant of Schlumbergera xbuckleyi "Rollinsonii", a Christmas cactus, since 1961. I named it "Junior." Last week I talked of Junior's history (link). Here I am going to describe what I learned from Junior about growing Christmas cacti and getting them to flower.

Christmas cacti like Junior are quite tolerant of not being watered but will rot easily if too moist. They never have much of a root system. In nature they perch on a tree as an epiphyte. You don’t need well-developed roots up on a tree branch. 

They root easily if you bury a joint between the segments in soil. That too probably harks back to life in the trees. If a piece that broke off can root, it helps maintain the plant in a dangerous world. Many other cacti easily root at the joints as well.

Christmas cacti like nice rich soil. --When they can get it.-- I’m not very good about fertilizing house plants. Junior gets fertilized, but maybe twice a year. I have been steadily giving it a bigger pot as it expands, so there are some nutrients added with the soil of the new pot. Junior's growth despite my benign neglect suggests it doesn’t need a lot of care.

Comments online said "bright light but not full sun." I didn't do that on purpose, but that fits my front window. It gets direct sunlight only early in the morning. A north-facing window works well, if you have one. (South-facing in the Southern Hemisphere).

The plant survives easily if not over-watered, but successful flowering is another matter. 

Draughts and sudden changes in its environment often cause buds to drop off. With a plant that has spectacular flowers once a year, losing the buds can be very discouraging. In the fall, put the plant in a spot that is bright by day and cool by night, where no heating vent or door causes a draught, and leave it there until flowers are almost open.  

Cool nights and warm days are recommended for good flowers on a Christmas cactus. I keep my house pretty cool at night in winter, and I do think that supports or enhances flowering. 
Clone of Junior that flowered in January 2014
Clone of Junior that flowered in January 2014

Christmas cacti flower in winter, hence the name. Junior’s buds can often be first seen in late November and frequently the first flower is open about December 17. This can vary a lot. I currently have two little plants that are also Junior, rooted from cuttings, on the laundry room windowsill. (Big Junior has the front picture window.) This year Junior had open flowers before December 17, but one of its clones opened its first flower January 6. The other had no buds at all this year. Same genes, different environments.

Clone of Junior that did not flower in winter 2013-2014
Clone of Junior that did not flower in winter 2013-2014
Christmas cacti are “short day” plants. That is, they flower when the days are shorter than the nights (or get shorter each day, in some species). In nature, day length is a very reliable cue:  it reports the changing of seasons without fail. Other indicators, like temperature and rainfall, can be very different in different years. For tropical plants, shortening days unerringly indicate the change of dry/rainy seasons. In temperate regions, shortening days warn of winter. 

Outdoors, day length changes happen and the plants respond accordingly. Extra light created by humans--street lights, porch lights and lights from signs, for example--all can confuse plants that rely on day-length cues. On a subtropical beach some winter, compare flowering in poinsettias, another short-day flowering plant, near and far from street lights. 

Indoors, artificial light that make the days as long or longer than the nights will turn off the processes in Christmas cacti that lead to bud formation. Thus, to flower, a Christmas cactus has to be kept in a room where it gets dark when the sun goes down. I don’t think they are really picky—a single blast of light won’t ruin everything—but they won’t bloom in a room that is frequently lit in the evenings. Florists put Christmas cacti and poinsettias in closets at the right time each night. I just find a less-used room.

I have been told to withhold water in the fall for a month or so and then start watering pretty heavily about November 1 to induce flowering. For Junior, that doesn’t matter. I water lightly twice a week, all year, and Junior blooms abundantly. 

"Junior" in bloom this year
"Junior" in bloom this year.
Many plants create more buds than they have the energy to mature as flowers or seeds. Those extra buds are insurance in case some buds are damaged. Consequently it is not unusual for the smallest buds to drop off without opening. It could be because of some kind of draught but it may simply be that the plant used all the energy allocated for flowering on the earlier flowers and so had to give up on the last ones.

Paul's Notes give a lot of good information on the group that matches my experience with Junior.

I've seen Christmas cacti a whole lot bigger than Junior and clearly they can live to greater ages. I certainly recommend them as house plants. 

Comments and corrections welcome.

Kathy Keeler

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