Christmas cacti sprout cascades of blooms in shades of pink, red, white, purple, or orange from late October to December. Schlumbergera were originally found in the rainforests of Brazil in the early nineteenth century, living high up in the trees amongst orchids and bromeliads. These epiphytic cacti need more water and less light than your average cacti.
Soil & water & fertilizer
Just like your average houseplant, water thoroughly and re-water when the top of soil starts to feel dry to the touch. Keep the soil evenly moist; don’t let the soil become waterlogged or dry out completely.
These cacti don’t need much fertilizing. Feed your Christmas cactus 2 to 4 times a year. Start fertilizing in early spring with one quarter strength soluble fertilizer and space out feeding until the end of summer. Stop fertilizing in the fall.
Repot the plant one size up every three years — as the Christmas cacti bloom best when kept somewhat pot bound. Christmas cacti’s natural habitat consists of leaf and bark compost, so use only well-draining potting soil.
Light & temperature
As an epiphyte, these cacti prefer indirect bright light in the winter and half shade to shady outdoor conditions if you take them outdoors in the summer. In bloom, these cacti thrive at room temperature, with an ideal range between 18 and 24 degrees Celsius, with flowers lasting at the cool end of the range.
Although the cacti are easy to keep alive, flower buds frequently drop. The main causes of spontaneous bud drop include hot air from vents blowing over plants and moving the plant to a new location. Other factors like drafts, overwatering, and temperatures below 10 degrees Celsius could also trigger bud drop.
Getting the Christmas cacti to bloom every year is easy. Christmas cacti are thermo-photoperiodic. Huh? It means flower buds are set with a combination of day length and temperature. In the cacti’s case, flower buds are set when:
Day length: day equals night (i.e. 12 hours light, 12 hours dark)
Temperature: exposing cacti to 10 to 15 degree Celsius (50 to 60 degree Fahrenheit) for a week or two.
Since my backyard is so dark, I just leave the cacti outside all summer long, and bring them in before night temperatures start to fall below 10 degree Celsius (50 F). I have fantastic blooms every year.
The old gardening practice of letting plant dry out as a “resting period” in early fall to promote more blooms has been proven untrue. The “dry down” treatment actually reduces the number of blooms on each “leaf” by 60 per cent.
With proper care, your Christmas cacti may last over 20 years. How’s that for a paradoxical plant?