Christmas and cactus may seem to be a contradiction of terms.

But Christmas cacti are among the easiest, showiest, holiday houseplants you can grow.

And yes, despite their succulent appearance and lack of spines, they are a cactus, and they do bear their sparkly, iridescent flowers during Christmas.

What’s more, they’ll live for years. Certain specimens are said to be 75 to 100 years old.

So start a new family tradition. Instead of exchanging a much-maligned heirloom fruitcake, propagate a Christmas cactus that will last from one generation to the next, spreading throughout your family tree.

Getting Started

Much of the year, Christmas cacti are rather quiet, with their jointed, olive-green stems clumped neatly in a pot.

But come November, buds begin to swell at the tips of those stems, then billow out into flowers linked in a series of colorful, glistening tubes. The shimmery shades of pink, purple, coral, red and white are the result of more than 150 years of breeding between several species of the genus Schlumbergera.

Christmas cacti are native to Brazil, where they grow north of Rio de Janeiro in the Organ Mountains. They’re epiphytes, meaning they pull moisture and nutrients out of the air. In nature, they grow in cracks between boulders or in decomposing leaf litter caught between branches of trees.

It’s surprisingly easy to replicate those conditions on the Central Coast.

For starters, mimic the forest canopy by providing bright light, but little direct sun, especially during summer. A lattice-covered patio or a spot with morning sun and afternoon shade should be just right.

Then grow your Christmas cactus in a container filled with a fast-draining blend of soil, peat moss, coarse builders sand, vermiculite, pumice or even Styrofoam beads. Or, use a packaged cactus and succulent mix. Given that propensity for growing in leaf litter, your Christmas cactus is not likely to survive if you plant it in the ground.

Instead, the plants are often at their best in hanging baskets, where they get plenty of air flow and their stems and flowers can cascade over the sides. A bonus of that portability is that you can easily bring them indoors to enjoy during the holidays.

Flowering is triggered by sunlight and darkness. The plants need six to eight weeks in a spot that goes dark for 12 to 14 hours every night, with temperatures ranging from

50 to 55 degrees.

Some folks put their plants in a closet every night. But Christmas cacti can be finicky about being moved frequently, and react by shedding their buds. An alternative is to leave your plants in place and cover them with paper bags at night.

To make absolutely sure your plants will bloom at Christmas, you should have started your light control in October.

However, on the Central Coast, our natural cycle is close to perfect. Outdoors, your plants already will have had the benefit of cooler temperatures. As long as they don’t sit within the direct beam of an all-night street light or patio light, they should bloom in December all on their own.

Regardless, once flower buds do appear, it’s fine to move your plants indoors. Inside, give them bright light, or even a bit of direct sun, and daytime temperatures between 60 and 70 degrees. Keep the soil barely moist and pinch off spent flowers.

After Blooming

Once all the blooms fade, move your Christmas cactus to a cool room or outdoors to rest. Be sure to protect the plant from frost and freezing temperatures. The cactus may melt away if temperatures drop to the low 30s.

Let the soil go dry between waterings. Don’t ever let the soil stay soggy, especially during cooler weather, as root rot can be lethal. But if the fleshy stems show signs of shriveling, water right away.

Some store-bought Christmas cacti are planted in a soil mix composed primarily of peat moss. While peat moss offers quick drainage, it’s difficult to rewet if it dries out. If you see the soil mix shrink away from the inside of the container, that might be the problem. If so, submerge the pot in a tall bowl or saucepan of lukewarm water for half an hour to saturate the peat moss. Then, drain the pot thoroughly.

Move your Christmas cactus outside once any danger of frost has passed. The plant may bloom again between March and May. But wait until active, green growth begins in the spring before fertilizing or pinching any errant stems to maintain the overall shape.

The growing season is typically from April through September, or when daytime temperatures range between 70 and 80 degrees. You can fertilize with a mild, water-soluble solution once a month during that time.

Finish any pinching back by mid-June. Any snipping after that will be at the expense of flowering at the end of the year.

There’s no need to repot your plants unless they begin to push up and out against the sides of their containers. If it is time to repot, wait until fall, when the growth slows down. Take care to avoid knocking off any emerging flower buds.

Beware of heat in October, which can cause the buds to drop. Buds also can fall off if the plants are subjected to major shifts in temperature, light or irrigation. If few buds even form, the cause may be too little water, too much cold or too much heat. If your plants look pale or yellow, they may be getting too much sun.

Propagation

It’s easy to make more Christmas cacti. Just pinch and twist a stem at its top joint, then pull it free.

Commercial growers typically take cuttings right after the first of the year, then grow them in greenhouses. But it’s a lot less trouble to wait until the weather warms up in late spring or early summer. Ideal temperatures for rooting are between 70 and 75 degrees.

If you’re shaping your plants at the same time, you can pinch off a stem containing up to four segments. Let your cuttings sit a few days in a cool, dry place, then bury about a quarter of the bottom segment of each in a loose, fast-draining medium.

Give the cuttings bright light and even moisture. You should see signs of life within several weeks. Commercial growers expect a new tier of growth every six weeks, but your results may vary. Water your new plants about once a week. As they grow larger, let the top layer go dry, as under-watering is better than over-watering.

WHAT’S IN A NAME?

*  Those who split botanical hairs may insist that what we see labeled as Christmas cacti are actually Thanksgiving cacti.

*  This line of reasoning holds that the only true Christmas cactus is Schlumbergera x buckleyi, a cross made by William Buckley in England in the late 1840s. That particular cross bears little bumps, rather than points, along the stems. Its flowers dangle, rather than curve outward. And, when given the same treatment, it begins blooming about a month later.

*  But to most people, the plants and flowers of all the many offspring of the genus Schlumbergera look nearly the same. The care is the same, too, as well as the general timing of the beautiful blooms. Given the countless crosses and permutations of the various Schlumbergera species, the terms Christmas and Thanksgiving hardly seem to matter.

SEEDS OF WISDOM:

*  Don’t toss your Christmas cacti after the holidays. The brilliant plants are definite keepers. Provide bright, indirect light, let the soil dry out between waterings, and your plants may live for generations.

Joan S. Bolton is a local freelance writer and garden designer. Her In the Garden column appears biweekly. She can be contacted through her Web site: www.santabarbaragardens.com.