The 12 days of Christmas plants -- Christmas cactus

How to grow Christmas and Thanksgiving cactus and get them to bloom.

This is the time of year when even people who rarely grow houseplants buy or receive gifts of flowering holiday plants -poinsettias, Christmas or Thanksgiving cactus, cyclamen, and others that are just as colorful but may not be as familiar.  How long do they typically last at your house -- till way into the new year or not even till the end of December?

If they don't live up to their potential, it's usually because the plant wasn't in good shape to begin with or it wasn't given the care it longed for. So, over the next two weeks, Diggin' It will be looking at how to keep the common holiday gifts plants not just alive but flourishing.

Today we'll start with Christmas and Thanksgiving cactuses (or cacti, if you prefer), nice homey plants that are usually kept instead of being tossed after the holidays.

In fact, they often are so long-lived that they're handed down from generation to generation, growing larger and larger. (My mom had one that was more than three feet across -- what a show it put on when it was in flower!)

You can tell the difference  between the two holiday plants by looking at the ends of the leaf segments.

If they're rounded, it's a Christmas cactus (Schlumbergera x buckleyi). If the ends are claw-shaped or more pointed, it's a Thanksgiving cactus (Schlumbergera truncata), which, true to its common name, blooms about a month before the Christmas cactus.

They're both easy to grow -- provided you don't overwater -- but sometimes they may be a  bit difficult to get to bloom when you want them to. There are a few tricks to accomplish that. More in a minute.

First, a little general care: Both types of plant like fast-draining soil and bright light but little sun. (If the stem segments start to turn red, the plant receives too much sun. Move the plant to a shadier spot.)

Water when the soil becomes just dry to the touch. (Since these aren't true cactuses, don't let them go long periods without no water, though.)

Christmas and Thanksgiving cactuses are fairly casual about fertilizer. You can feed them once or twice a month -- except for the month before they bloom -- if you fertilize all your other houseplants.

Or most don't seem to mind almost never being fertilized, provided they're in good shape and otherwise receive the proper care.

They thrive in average household temperatures, but can't tolerate frost if you're late bringing them indoors in fall after a summer outside.

Actually, though, leaving Christmas and Thanksgiving cactus outside till temperatures fall into the mid-50s is one way to encourage the plants to bloom.

Along the same line, I leave my favorite Thanksgiving cactus on a wide windowsill in my drafty Victorian row house, giving it a one-quarter turn each week. The chilly air causes buds to form so that, as usual, it bloomed right on schedule this year.

Admittedly, it's easier to get a Thanksgiving cactus to bloom than a Christmas cactus.  What  I do with those is  give them 12 to 13 hours of complete darkness each day until flower buds form -- usually four to six weeks.

That can mean putting the plant in a closet or spare bedroom each night and removing it the next morning. Or putting it under a cardboard box every evening. The main thing is that the darkness has to be continuous -- no turning on the lights late at night or early in the morning.

But you can't just plop the plant in the dark and forget about it -- it still has to have 10 to 12 hours of light each day.

Some gardeners think that it's a good idea to cut back on watering a little while you're trying to get the plant to set buds. That's not a bad idea. But you don't want to  overdo it. If the thick leaf segments start to look shriveled, water.

I also stop fertilizing in fall -- until after flower buds have formed.

So there are two ways to get a Christmas or Thanksgiving cactus to bloom:  Place the plant where temperatures are about 55-58 degrees. And give it 12 or 13 hours of darkness. If one doesn't work, try the other.

You get such a nice feeling of satisfaction when the flowers finally open. They're not necessarily exciting or glitzy (well, maybe those fuchsia ones), but a quiet, old-fashioned welcome to the season.