by Emma Murphy, Master Gardener
Definition of conundrum
A confusing and difficult problem or question
Despite the shortening days and dark and dreary November weather, every year around this time I am delighted to see members in my various gardening groups posting photos of their “Christmas cactus” in bloom. The colours are many and varied – from red to pink to white to some lovely peach selections. People post amazing stories of plants being handed down from generation to generation and being over 100 years old.
The conundrum? They are generally not “Christmas cactus”. Since education is a big part of the role of Master Gardeners, I thought I would offer some explanation of the various types of indoor cacti we see here in Ontario (and Canada) and how to figure out what type of cacti you have!
There are actually three types of holiday cacti – all theoretically named for the time of bloom (although that gets messed up depending on whether you are north or south of the American/Canadian border!). The three types are:
- Thanksgiving Cactus (Schlumbergera truncata)
- Christmas cactus (Schlumbergera bridgesii [also S. buckleyi])
- Easter cactus (Rhipsalidopsis gaetneri [also Hatiora gaertneri])
They are all called “leaf cacti” because the plant bodies are flattened and the leaves are actually stems. These type of cacti are epiphytes from the tropical treetops of the rain forest and natural forests of Brazil and require similar care, even though they bloom at different times of the year. In their natural habitat, they grow on trees or rocks in habitats that are generally shady with high humidity, as opposed to their desert-dwelling cousins. So they don’t need bright sunlight and they don’t have nasty spines!
Most people have the Thanksgiving cacti, which bloom between November and January. Christmas cacti bloom in December, and Easter cacti in April/May.
The leaf stems (and to some extent the flowers) tell you which type you have, rather than the bloom time. Thanksgiving cactus is often known as “lobster cactus” because the edges of the leaves are hooked, giving them a claw-like appearance. The Christmas cactus has leaf projections which are more scalloped or tear drop shaped. The Easter cactus has very rounded edges which are centralized on the leaf.
All three cacti are short day plants, so in order to induce the plant into bloom it must have 12 to 24 hours of darkness and cool temperatures. If you have put your plant outdoors over the summer or purchased it recently it should be kept in a cool, dark location until it sets buds. A seldom used bedroom or lower level is the ideal place. The Christmas and Thanksgiving cacti require approximately 6 weeks of short days in order to bloom (the Easter cactus requires 8 to 12 weeks to bloom). When the buds appear it can be brought into a warmer area. If it starts dropping buds it could be due to drafts, too-warm temperatures, too much water or direct sunlight.
FUN FACT! Unlike Christmas poinsettias, Christmas cacti are not toxic to dogs and cats, making this cat mum very happy.
Since they are from the rainforest, they like acidic well drained soils. Use a cactus mix and add perlite, vermiculite and orchid bark. Do not overwater – why most of them die! Neglect is better than over watering. Water when the top 2 inches of soil is dry. Mist them frequently to increase humidity and fertilize them with a all purpose fertilizer. Those who hate repotting plants can take comfort in knowing that holiday cacti bloom best when they are slightly pot-bound and only need repotting every 3 or 4 years.
The most common issue you might face is dropping buds, which can occur when there is any type of change in the temperature, lighting, humidity, or the amount of water the plant is receiving. Try to keep the soil moist, the temperature a steady 15 to 20 degrees Celsius, no fertilizer in the late summer to fall months, and 14 hours of darkness each day. Other issues that could affect your cactus include stem rot (this fungal issue occurs when the soil is too damp – start a new plant before the infection spreads too far), root rot (happens if roots get soggy, so remove that root so it doesn’t go further up the stem, which might kill the plant), and Botrytis blight (which is grey mold and can be removed if discovered early).
When they have finished blooming, these cacti need at least two months rest. Give almost no water or fertilizer during this time. The Thanksgiving and Christmas cacti may bloom again in the spring, but probably with less (and smaller) blooms.
While holiday cacti appear to be a bit finicky, if you understand where they come from, and what they need to be happy, you may be able to successfully keep your holiday cactus for 100 years!