Plants give me a lot of peace; having them around me allows me to unwind. I have been a horticultural advisor with the Royal Horticultural Society for more than 12 years and during that time, one of my favorite winter indoor plants has become Christmas cacti, formally known as a schlumbergera. Others include the amaryllis, because they have large, exotic flowers. I also love spring outdoor bulbs such as hyacinth which flower indoors at Christmas, and have a fragrance that I really enjoy.
A Christmas cactus is an epiphytic plant, which means that it grows in pockets of organic material on trees in humid tropical rainforests in South America. What makes a Christmas cactus unique is that its exposed position in the canopies of the trees means the water within it drains away quickly. It also doesn't grow on the ground as other terrestrial cacti do.
Despite their differing habitats, Christmas cacti and other terrestrial cacti have similar challenges: to capture and store rainwater in their tissues in order to survive. Christmas cacti flower in November and December in the northern hemisphere and are also referred to as the Thanksgiving cactus in America.
1. Lighting a Christmas cactus
In order to produce flowers, Christmas cacti respond to the shortening daylight hours in autumn. I have found that if you keep a Christmas cactus in a room with artificial light, such as a sitting room, you'll find that it won't bloom. This is because the plant confuses artificial light with sunlight, so it tends to "think" that the days are not getting shorter and won't form buds.
Therefore, in order to get a Christmas cactus to bloom, it would need to grow in a room with no artificial lighting, ideally on a bright window ledge, but one which does not receive direct summer sunlight. This is because Christmas cacti grow in nature where they are shaded by the canopies of their host trees, and they haven't evolved to handle direct summer sunlight well, so they would invariably scorch.
I would place a Christmas cactus on a south-facing window behind a net curtain or a west-facing window without protection. It's also important to note that you should not move the plant once it has begun to set buds, as it may cause it to stop growing.
2. Watering a Christmas Cactus
In nature, the roots of Christmas cacti don't dry out for long periods like ordinary terrestrial cacti, so a Christmas cactus should be watered more frequently.
To water a Christmas cactus, it is best to use rainwater that is kept at room temperature or filtered water that is produced by a reverse osmosis filter.
Rainwater can be collected by diverting it from a drainpipe into a water butt. This would need to be at room temperature before watering a Christmas cactus. A reverse osmosis filter is a piece of equipment that can be attached to your tap and will purify and filter harsh chemicals out of the tap water. The treated water can then be collected and stored for future use.
Water quality is important because Christmas cacti, in common with most other epiphytic plants, prefer an acidic compost. Tapwater can be alkaline, which would then make the compost's pH unsuitable for the plant's health.
Watering the plant correctly will allow it to grow, as Christmas cacti thrive in acidic soil. When you repot a Christmas cactus, I would advise repotting it with ericaceous compost, as it has a low pH balance. It is also helpful to improve drainage by adding some extra perlite in a ratio of three parts ericaceous compost to one part perlite.
Christmas cacti are generally tolerant plants, and I have found that the key to ensuring that they survive is mainly down to how well you water them. Christmas cacti should be watered once the potting soil is approaching dryness and never when the soil is very moist. It's always best to wait until the compost is almost dry before watering a Christmas cactus, rather than watering it routinely. Keeping the soil too wet by watering a Christmas cactus frequently can result in the roots rotting.
Any excess water should be allowed to drain from the bottom of the pot and then immediately discarded. I have seen Christmas cacti that have remained too wet for too long which has resulted in their roots rotting. But sometimes, the plant can be rescued by taking cuttings from healthy upper parts of the stems.
3. Feeding a Christmas Cactus
Christmas cacti benefit from being fed with a regular houseplant fertilizer during the growing season, from April to the end of September. Beyond that, my experience with these plants suggests that you should stop feeding your Christmas cacti until the following April. That's because light levels are low in the autumn and winter in the northern hemisphere, which stops the plants from growing.
It's also best to keep a Christmas cactus at a room temperature of around 65 degrees fahrenheit because it is a tender plant. If Christmas cacti were subjected to cold temperatures and snow, it would kill them.
Rob Stirling has worked with plants for over 30 years. He works at RHS Garden in Wisley, Surrey. In February, they will be holding an imaginative exhibition showcasing wonderful varieties of plants. You find out more information about it here.
All views expressed in this article are the author's own.
As told to Newsweek associate editor, Carine Harb.
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Uncommon Knowledge
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
