Christmas Cactus

If you’re the proud owner of a flowering cactus, you’ll find they’re carefree plants that add color to grey winter days. (Photo: Shutterstock).

Carol O'Meara, Colorado State University Extension

Carol O’Meara, Colorado State University Extension

Did the spiky showoff with brilliant pinks, purples, and reds catch your eye as it dangled from a hanging pot in the local greenhouse? If you’re the proud owner of a flowering cactus, you’ll find they’re carefree plants that add color to grey winter days.

“The three cactus types, Thanksgiving (Schlumbergera truncata), with pointed “teeth” on the stems, Christmas (Schlumbergera x. buckleyi), with rounded tips and Easter cactus (Hatiora gaertneri), are actually epiphytes. They live in trees in their native Brazil like orchids, but we grow them in pots here,” says Dr. Steve Newman, greenhouse crops specialist with Colorado State University Extension.

Although they’re cacti, they don’t grow dry; water yours weekly as the top inch of soil gets dry, and provide it with half-strength fertilizer each time you water. Every third week, give it clear water instead. “Because no one likes to stain furniture or carpeting, most people water without letting it run out of the bottom, and salts build up in the soil. Put the pot in the kitchen sink or bathtub every third watering and let water run though to flush salts out,” said Newman.

Avoid drafty areas for your cactus – chill blasts aren’t good for it. “But the challenge for large Christmas cactus is keeping it out of traffic areas. Sections fall off whenever people brush against them.”

The good news is that these sections are easy to root by placing them in a glass of water, and when the roots come out, pot up the section in sterile, everyday potting soil. While young, the small plant should be guarded against overwatering, so before you give it a drink, check the soil to be sure it’s not wet.

To have your cactus bloom for Thanksgiving or Christmas next year and each year thereafter, mark your calendar for September 19 as the date to begin the reblooming process. “Living around the 40th parallel as we do, that’s the date to start stimulating plants so they’re blooming in time for Christmas,” says the 25-year veteran of greenhouse growing. “Poinsettias and cactus – two popular flowering plants – are treated this way.”

A combination of cool temperatures and darkness is the cue these plants need to bloom, so move the cactus to a place with cool, 60-degree nights and only nine hours of sunlight daily.  After approximately six weeks, Thanksgiving cactus will flower, and after two to three months, Christmas cactus blooms.

The secret to eye-popping color is reducing water to the plant after flower buds have formed, says Newman. Water weekly until after the flower buds begin to swell, then cut back on the water slightly, letting the cactus dry out between watering without getting bone dry. Blossom color intensifies if the plant dries once flowers start, he said; many growers finish flowering plants this way during the last two to three weeks before they go on sale.

Be aware that too dry will abort the flowers, so to avoid it going too far, get to know your cactus soil by inserting your finger in it up to the first knuckle, just before watering.  Note that moisture level; as you dry down your cactus, check the soil to gauge when it’s a bit drier but not parched. “This is the best water meter ever invented,” says Newman, holding up his hand and indicating the tip of his index finger.

As flowers unfold, move it out into the room where you want to display it, keeping it in bright, indirect light. A cool room is best; too much heat can cause flowers to fade and drop quickly, and if the leaves wrinkle, the plant is too dry or too warm.  There’s no need to feed it during blossom, but after flowering, return the cactus to normal care of fertilizing at half strength and water weekly.

By Carol O’Meara. Colorado State University Extension, together with Boulder County Parks and Open Space, provides unbiased, research-based information about consumer and family issues, horticulture, natural resources, agriculture and 4-H youth development. For more information contact Colorado State University Extension at the Boulder County Fairgrounds, 9595 Nelson Rd., Box B, Longmont, 303.678.6238, e-mail comeara@bouldercounty.org or visit ext.colostate.edu/boulder.