Sage Advice

Christmas Cacti

Callum Halstead

I’m sure many of us will remember Christmas Cacti from our childhoods. At one time or another, our parents or grandparents will doubtless have had a brightly coloured specimen growing at home— for some reason usually displayed in the window of the downstairs loo, leaves tinged red from too much sun. Then, for some reason, towards the end of the twentieth century, these little plants fell out of fashion. As we all retreat inside during these darker months of the year, I thought it would be timely to revisit these fine old houseplants to see what we’ve all been missing. To that end, I paid a visit to my good friend and Schlumbergera collector, Gunnar Ovstebo. Originally from Norway, Gunnar now lives in Edinburgh where he works at the Royal Botanic Gardens, caring for the glasshouse collections. In his spare time, he collects and breeds Schlumbergera, proving to anyone fortunate enough to see his spectacular collection that this once popular but now slightly overlooked genus is more than overdue a revival.

The first thing I like to do whenever I visit Gunnar’s home is to stand at the foot of his tenement stairwell and look up. Spiralling up to the skylight in the roof above me, overhanging the banisters and thriving in the cool conditions, are tier upon tier of Easter, Thanksgiving and Christmas Cacti. Walking up the stairs, it’s easy to imagine I’m rising into the canopy of the Brazilian cloud forests where Schlumbergera are naturally found. It can take quite some time to get to the top; not because it’s a particularly tall building, but because it’s impossible not to stop to marvel at all the different shapes and colours of these spectacular plants. With each flight, the display grows more dense, luscious, and verdant.

Gunnar started growing Christmas Cacti after he was given a cutting from his mother’s plant, which had originally been handed down from his grandmother. He had grown up with this plant in his family home and taking cuttings to grow on felt as important as the continuation of any other family tradition. Even after amassing a collection of hundreds of different varieties of Schlumbergera, it is still the plants grown from these cuttings that remain the most important to him, and to which he feels the most enduring attachment.

The Christmas Cactus, as it is known, is the product of two species of Schlumbergera (S. russelliana and S. truncata), and the resulting hybrid is known as S. x buckleyi. Despite their name, these plants tend to flower early in the new year in the UK, usually through January into February. If you think you already have a Christmas Cactus but have been left scratching your head after it has finished flowering long before the start of December, it could be that what you actually have is an Autumn or Thanksgiving Cactus. These tend to have more S. truncata in their breeding, so start flowering a little earlier in the season. A good way to tell what’s what is to look at the margins of the ‘leaves’ (they are actually modified stems, called phylloclades). Thanksgiving Cacti tend to show more toothed margins, while those of Christmas Cacti tend to be more rounded. You might also see plants being sold as Easter Cactus. Although these are closely related, they belong to a different genus altogether— Rhipsalidopsis.

Quite the latest thing in the world of Schlumbergera is a sub-group of crosses, known as ‘Queens’. These are a cross between S. truncata and another species called S. orssichiana and sport flowers that are considerably bigger, bolder and even more fabulous than any of the other varieties mentioned here. In some cases, they have more than one flowering season, too.

Interestingly, the colour pigments found in Schlumbergera flowers are the same as those found in Beetroot (Beta vulgaris), which is why they inhabit the hotter end of the colour spectrum with pinks, reds, oranges and yellows all available. A little rarer, and therefore highly sought-after, are the albino cultivars with their pure white blooms.

Many of the best and most prolific breeders of Christmas Cacti are based in Europe, primarily in the Netherlands. Regrettably, the current state of relations with the EU makes it extremely difficult for houseplant enthusiasts to buy plants directly from the continent without having to pay through the nose for the privilege. A good place to start your collection, therefore, would be at a local supermarket, garden centre or perhaps one of the new houseplant shops that have recently started springing up across the country. You’re unlikely to find anything too unusual here, but they will often stock a nice selection of attractive colours to get you going. For those after something a little more select, Facebook (Meta) groups such as ‘Schlumbergera-Rhipsalidopsis-UA’ offer members opportunities to trade and buy plants from one another.

Some excellent varieties to look out for include S. ‘Purple King’, S. ‘Sonja’ and S. ‘Dutch April’. These are all quite similar in look, with pinkish-purple blooms and quite an upright growth habit. All are very strong growing plants that can be more readily relied upon to flower exactly at Christmas.

© Callum Halstead

Once you have a collected a few different Schlumbergera, it is very easy to start creating your own crosses and this is exactly what Gunnar has been doing for the past few years. It’s easiest, of course, to cross plants that are in flower at the same time. However, it is possible to collect and freeze pollen for use later if you fancy a bit more of a challenge. You’ll know if it hasn’t worked as the flower and ovary will wither and fall off, but if your cross has been successful, the ovary will swell and turn a pink or reddish colour, looking rather like a jellybean. It will take five to seven months for the fruit to ripen, so some patience is required. Once the fruit has ripened, it will start to soften and at this stage the seeds can be removed and dried on a piece of paper for a few days. Then sow a few dozen seeds on the surface of a small pot of sterilised seed compost. Cover the pot over with cling-film to create a tiny greenhouse-like environment, which you should then keep moist but not too wet. Once germinated, the new plants can be kept in this pot for quite some time, so don’t feel that you need to pot them all up immediately.

Few young plants look as endearing as Schlumbergera seedlings. At Gunnar’s house, the sight of these alone was enough to spur me to cross-pollinate my own plants as soon as I got home. You won’t truly know what you’ve got until the plants flower for the first time, which can take two to three years. Reassuringly though, it is apparently rather difficult to breed a Schlumbergera that doesn’t have incredible blooms. Perhaps as a result, the focus of Gunnar’s breeding efforts has been on creating plants that also have interesting foliage. This makes sense because for nine to eleven months of the year, depending on the plant, it is the leaves and not the flowers that will be on display. Earlier this year, Gunnar registered his first hybrid, S. ‘Brightlingsea’, a plant that not only has handsomely toothed foliage, but also produces large, fiery, two-tone flowers whose petals are a beautiful golden yellow, suffused with cinnabar tones at their margins.

When growing your own, a cooler room will certainly be preferable to a warmer one. The next consideration is light. Variations in light quality in different parts of the home can often pose something of a challenge to people who are new to growing houseplants. It can take some time to figure out exactly the best spot to achieve optimal growth, regardless of the type of plant you are trying to keep happy. It is important to remember that although Schlumbergera are adapted to grow in a shady environment, this does not mean that they can do without light; the shade cast by a forest canopy is not the same as the shade of a windowless boxroom. Bright, indirect light is best and placement within a metre or two of a north or east-facing window is usually optimal. Better still, below a large skylight if you happen to have one. Fortunately, Schlumbergera are very forgiving of poor placement and will let you know that they’re a bit unhappy about where they’ve been placed long before it’s terminal. Too close to a sunny window in summer and the plant’s leaves will turn red, especially if they’re also a little thirsty, so simply move the plant slightly further away from the window, give it a good drink, and it should perk up. If the plant is not getting enough light, it’s not quite so obvious, but flowering will generally be reduced, and growth will be slower and quite one-sided as the plant reaches towards the light. Good growing partners for Schlumbergera that will thrive in similar conditions include Aspadistra spp. (Cast Iron Plant), Clivia spp. (Natal Lily), Haemanthus albiflos (Paintbrush), and Rhipsalis spp. (Mistletoe Cacti), as well as some bromeliads such as Aechemea spp.

Almost all Schlumbergera will grow into large plants if you let them. Mature specimens can reach nearly a metre across; very impressive if you have room. Where space is at a premium, and particularly if you have a lot of other house plants jostling for position, it is quite easy to restrict their growth simply by keeping the plants in small pots and, in effect, ‘bonsaiing’ them. Schlumbergera respond well to feeding, particularly if they’ve not been repotted in a while. Gunnar has achieved good results using Phostrogen All Purpose Plant Food. This can be an effective way to bulk up young plants and improve flowering, but you can quickly end up with a monster on your hands if you over-fertilise.

As a new grower of Christmas Cacti, you will likely find that your main foes are Mealybugs. Prevention being easier than cure, it’s always wise to check any new plants for hitchhikers, to avoid starting a colony of pests in your living room. If they do strike, spray the affected plants with SB Plant Invigorator, which will help to control the wee beasties, while also acting as a foliar feed to give your plants a bit of a boost.

When it comes to sharing your plants with friends and family, or indeed replacing plants that have outgrown your space, it’s quite straightforward to take cuttings of Christmas Cacti. It is possible to root entire branches, however a cutting that is two to three segments long will usually result in a better and more balanced plant. To take a cutting, break off the section that you want to propagate at the join where two segments meet and leave it in a cool, dry place for a few days for the wound to callus. After this, the cutting can be potted, with its bottom segment half submerged in the compost for stability. Gunnar favours Melcourt SylvaMix peat-free potting compost. However, almost anything can be used as long as good drainage is maintained. It’s best to avoid anything too ‘heavy’ or loam-based, like John Innes, but counter-intuitively this also rules out cactus and succulent composts. Place the pot somewhere cool and bright and water sparingly until you see new growth starting to form.

If I have at all tempted you into starting to grow Schlumbergera, then it would be remiss of me not to point you in the direction of www.schlumbergera.net. This fascinating website offers all sorts of useful resources for budding growers, including more detailed growing advice and an expansive list of wonderful cultivars to help you grow your own collection. Finally, my thanks to Gunnar Ovstebo for sharing his collection with me, and his wisdom here.