Nudge Christmas cactus to bloom on time: Coaxing cyclamen

One of the most popular flowering houseplants during the holiday season often provokes a number of questions: Why didn't my Christmas cactus bloom this year? Why does it usually flower before Thanksgiving instead of at Christmas? What makes it sometimes bloom twice a year?

The answers are easy once you know more about these plants and what causes them to flower.

Actually, there are three different plants that may be called Christmas cactus. The true Christmas cactus (Schlumbergera truncata) usually blooms in December. It doesn't flower as readily as Thanksgiving cactus (Schlumbergera russelliana). You can tell the difference between them because the tips of the segments are rounded on Christmas cactus, but claw-shaped on Thanksgiving cactus. True to its name, Thanksgiving cactus blooms in November. A similar plant that's known as holiday cactus (Schlumbergera x buckleyi) combines the best qualities of Thanksgiving and Christmas cactuses and blooms twice - in autumn and in midwinter.

But you can force any of these to bloom whenever you'd like by providing the conditions that cause them to form flower buds - temperatures below 58 degrees F. or 14 hours of darkness each day for a month. That's the reason plants that spent the summer outdoors and are brought inside in fall when nighttime temperatures drop into the 40s bloom early.

Some Christmas-cactus fans feel that watering the plants less in fall also causes abundant flowering.

But don't go overboard. If the segments look wrinkled, the plant isn't getting enough water. And if you put it in a dark closet each night, remember to move it back to good light in the morning. Also, make sure temperatures don't fall below 40 degrees.

A contrast to the easygoing Christmas cactus is another appealing holiday plant, cyclamen (Cyclamen persicum). With perky flowers waving like butterflies above heart-shaped, silver-veined foliage, it's an attractive plant - but best suited to experienced houseplant enthusiasts who have an unheated room with good light in which to place it.

Not only are chilly temperatures crucial to cyclamen success, so is watering. The plant grows from a corm (it looks like a flat bulb), which, if overwatered, rots. For this reason, some growers eschew the conventional watering technique. Instead, they put water in the pot's saucer and let the soil soak it up for 20 minutes so the corm doesn't get too wet.

At the other extreme, if a cyclamen doesn't get enough water, it completely wilts. When that happens, submerge the entire plant, still in its pot, in a bucket of warm water until bubbling stops. Place the plant away from sunlight for a few hours, and it should bounce back.

(c) Copyright 2000. The Christian Science Publishing Society