Is your grandmother’s pass-along Christmas cactus blooming really early? Do the leaf segments have “teeth” along the edges? Are the “stringy things” sticking out of the flowers yellow in color?
Well, I hate to tell you this, but that is not a Christmas cactus (Schlumbergera bridgesii). It is a Thanksgiving cactus (Schlumbergera truncata). You can tell the Thanksgiving cactus apart from the Christmas cactus by the shape of the leaves and flower anthers.
The leaves, botanically referred to as phylloclades, are serrated on the Thanksgiving cactus. Additionally, the pollen-bearing anthers in Thanksgiving cactus flowers are yellow. Christmas cactuses have smooth-edged leaves and pinkish-purple anthers.
Both of these species are native to the coastal mountains of south-eastern Brazil, where they are found growing in trees or on rocks. Therefore, the preferred potting media for Thanksgiving and Christmas cacti should contain about 40 percent perlite to ensure good drainage and aeration.
To care for your Thanksgiving cactus, allow the soil to dry out when it is not blooming. As flower buds develop, the soil should be moist to the touch. However, overwatering can kill the plant. Additionally, provide plenty of indirect light and temperatures of 60-65 degrees Fahrenheit.
Want to get last year’s plant to bloom again? Beginning in mid-September, it will need 12-14 hours of total darkness, along with cool (60-65 degrees F) nighttime temperatures for three to four weeks. To achieve the light control, the cactus can be placed in a closet or covered with a large brown paper bag overnight.
Once buds start to form, fertilizer can be applied to encourage growth and blooms. However, flower buds will fall off with any significant changes in temperature (below 50 degrees F), light or watering.
Now, if your “Christmas cactus” doesn’t set flowers until spring, it is probably an Easter cactus, a totally different species (Rhipsalidopsis gaetner). The leaf margins of Easter cactus have small bristles and are more three-dimensional, with a thick ridge on one side. Additionally, the flowers are more star-shaped than the other two cacti.
All three cacti species have flowers that come in a range of colors including variations of red, pink, peach, purple, orange or white.
Sheila Dunning is an agent at the University of Florida's Institute of Food and Agricultural Sciences Extension office in Crestview.