Christmas Cacti

Let’s just jump right into the facts about this unusual group of tropical plants.

Common name (Northern Hemisphere): Christmas cactus (and close relative, Thanksgiving cactus)

Common name (Southern Hemisphere): Flor-de-Maio

Scientific name: (Thanksgiving cactus) Schlumbergera truncata and (Christmas cactus) S. x buckleyi

Native home: Tropical rainforests of southeastern Brazil (Southern Hemisphere) where it grows as an epiphyte suspended from trees and rock surfaces.

Flowering time in native home: May (not associated with any holiday)

Flowering Time in Northern Hemisphere: Falls around Christmas, hence common name was quickly adopted as “Christmas cactus.”

What triggers flowering? Length of nights and temperatures. Thanksgiving and Christmas cacti, like poinsettias and mums, are photoperiodic. A flower-inducing hormone is produced in the plants’ stems, but light destroys the hormone, so even short bursts of light interrupt those dark periods and delay blooming. This is why it’s important that you keep your plant in a room that is dark overnight, but one that receives bright light during the daytime.

Simultaneous with that, lowering temperatures also hint to the plants that bloom time is approaching. The ideal indoor temperature for production of flower buds and to keep the flower parts looking fresh the longest would be 65F.

How to care for your plant: Keep it consistently moist. Even though it’s a true cactus, it’s native to a rainforest environment where it rains 100 in. per year. Good drainage is critical. Since it typically grows suspended from a tree trunk or other vertical surface, water (rainfall) drains away quickly. Use sphagnum moss to line a wire hanging basket or grow your plant in a terra cotta pot with a lightweight porous potting soil. Apply a diluted solution of a water-soluble plant food each time that you water your plant.

What about sun and temperature? Thanksgiving and Christmas cacti are shaded in their native homes. Give them no direct Texas sun, especially in summer. Protect them from freezing temperatures. Move yours indoors anytime the temperature is expected to drop below 40F.

How are they propagated? By stem cuttings of 2 or 3 segments stuck into very porous rooting medium (no topsoil). It should contain 25-30 percent perlite or sand.

You can also lay the segments on a shallow pot filled with the same potting mix you use to grow your cacti. Instead of inserting the stems, merely lay them on the surface of the potting mix. Keep the mix moist and roots will form and grow down into it. When they are 1/2-in. long you can dig the cuttings and pot them into 4-in. pots, 3 or 4 cuttings per pot.

Note: How can you tell Thanksgiving and Christmas cacti apart?
When they are blooming is an obvious starting point. You’ll get it right probably 90 percent of the time.

Stem segments of Thanksgiving cacti have points that make them look like claws. Christmas cacti stem segments are more rounded.

Thanksgiving cacti tend to be more upright, while Christmas cacti are more pendant.

Most plants sold in nurseries and gardening centers are Thanksgiving cacti.