How to Provide the Light Your Christmas Cactus Needs to Thrive

The Christmas cactus is an adaptable tropical, hailing from Brazilian rainforests and brightening the winter season across the hemispheres. In the Cactaceae family with desert-dwellers like Saguaro and prickly pear, Schlumbergera differs from its xeric relatives in its humid forest environment. With the right temperatures and lighting to initiate budding and flowering, they shine for weeks around the winter holidays with rich, billowy blooms.

Christmas cactus (Schlumbergera x buckleyi) is part of the holiday cacti lineup along with Thanksgiving cactus (S. truncata) and Easter cactus (S. gaertneri). Thanksgiving cactus blooms right in time with autumnal festivities, starting in November. Christmas cactus follows with its December show, leading into the Easter flowering season.

For Christmas cactus to put on a display for the holiday, special attention to light exposure, and especially day length, supports flowering. Beyond winter, the long-lived specimens grow as houseplants for decades, with the proper lighting as a key cultural requirement.

About Christmas Cactus

Christmas cactus takes center stage this season with a spectacle of bright, flared blooms and uniquely succulent, arching branches. Schlumbergera x buckleyi usually flowers for four to six weeks in time with the winter holidays, beginning in December and lasting through January. The saturated red, white, pink, purple, and coral hues stand out amongst its dark green backdrop and in the heart of winter. 

The holiday cacti group is easy to grow and offers year-round interest with their scalloped phylloclades (the leafy segments that make up the stems). In their native rainforests, the cacti live in the crooks of trees and crevices of rocks. They experience regular moisture and humidity, followed by seasonal dry spells. They grow beneath the broad tree canopy, experiencing dappled light and open shade.

To initiate budding in the fall, shorter day lengths and cooler temperatures are necessary. The cacti respond to longer periods of darkness (shorter days) to set buds and flower before entering dormancy. As we move our Christmas cactus indoors for overwintering (or as a permanent resident), the proper lighting is essential for the adaptable tropicals to thrive.

Moving It Indoors

Our favorite holiday tropicals perform well as houseplants, especially with summers spent outside before moving inside for winter protection and the bloom display. Outside of zones 9-11, Schlumbergera need shelter against cold conditions. Before making the move, they benefit from exposure to cool nighttime temperatures.

Bring them inside as temperatures drop consistently below 50°F (10°C). They withstand the 40s (around 4°C), but do best with protection against these lows to avoid cold damage. Exposure to cool temperatures goes hand-in-hand with optimal light for the Christmas cactus to flower.

In their mountain forests, they grow at elevations of 3,000 to 5,000 feet, with ideal daytime temperatures between 70-80°F (21-27°C). In winter, the nighttime temperatures are near 55-60℉. Cool nights promote bud development for blooming around the holidays.

Temperatures near 60°F (16°C) at night for several weeks, from about mid-September into November, promote bud set. Warm nighttime temperatures (70°F or 16°C or higher) for extended periods during this timeframe limit bud development or cause young buds to drop.

Indoor pots benefit from a cool room or space with natural light. If temperatures stay above 65°F (18°C) at night, compensate by adjusting the Christmas cactus’s light.

To Initiate Budding

Since the cacti respond to a cycle of cool nighttime temperatures and shorter day lengths to trigger budding, increased hours of darkness during the development period ensure bud set. For the four to six-week timeframe, the succulents need at least 12 hours of darkness each night to develop strong buds.

If nighttime conditions are warm, we can compensate with longer dark periods to make up for the lack of chill. If room temperatures are above 65℉ at night, try to limit Christmas cactus light hours to about 9-10. Coverage tricks can help provide longer nighttime hours (about 15 dark hours).

Lengthening Darkness

One way to increase the dark hours is to turn off the lights in the room early in the evening. This limits the amount of artificial light that lengthens the day in terms of plant responses.

To really make sure blooms are in place for the holidays, a light-blocking cover over the cactus at night does the job. For several weeks, cover the plants for the necessary hours of darkness to prompt a holiday bloom time.

A cardboard box or dark fabric creates a removable dark cover (taking care not to weigh down the stems and developing buds). Or, move the pots to a dark pantry or closet at night, returning them to their bright growing location during the day. Covering or moving them at night for about four weeks mirrors their necessary photoperiod.

Once buds form, the cacti can stay in their regular growing spot without additional darkness.

For Indoor Growing

During the day, Christmas cactus requires plenty of bright, indirect light for the energy it needs to grow and flower. Position their containers near a bright window, but out of intense direct sun.

An east or south-facing placement is ideal. From an east-facing window, they’ll receive ample morning sunlight. South-facing gives all-day Christmas cactus light.

Place pots a few feet from the window to avoid direct rays. A curtain or blinds, too, work as a filter. Too much direct sunlight, especially in the afternoon, can scorch stems and cause buds to drop.

Signs of Too Much Light

It’s normal for the cacti stems and phylloclades to turn shades of pinky-purple-red as seasonal conditions change and as we transition pots from outdoors to indoors. The blushing is usually a response to cool temperatures or too much light. The deeper tones aren’t necessarily a signal of intense distress, and even provide foliar interest, but to moderate the change, aim for consistent light and temperature.

Move the canopy-dwellers where they’ll experience bright, indirect light. Avoid the afternoon sun to limit discoloration and damage. Too much sunlight, too, can cause browning or blisters. Direct rays sunburn the leaves and scorch their tissues.

Keep the cacti near their ideal temperature range without letting them dip below the low 40s℉ before bringing them indoors. Average home temperatures are usually fine to support their development.

Not Enough Light

Too much shade can cause pale leaves, languid stems, and a lack of blooms. If the segments look slightly yellow or a pale green, move the container to a brighter location. Increased Christmas cactus light exposure can reverse the problem. Just take care not to overcorrect by moving the plant to direct sunlight.

If your Christmas cactus isn’t budding or flowering, it may be due to low light during the day. It could also relate to insufficient nighttime darkness, since they respond to shorter day lengths to develop buds. Bright light year-round offers the necessary resources for photosynthesis. The several weeks of 12-hour darkness set the stage for flowering.

After Flowering

Shortly after blooming for the season, Christmas cactus enters dormancy. Keep the containers in their bright position with indirect sunlight. No special tending is necessary during this rest period, other than occasional watering as soils feel dry.