Your gardening questions answered: How can I boost my Christmas cactus?

My flowering cactus was magnificent for Christmas, but now I have to wait for it to flower again. Is it possible to slip it? Or make it bloom again?

KR, Co Clare

Exotically colourful in flower and exceptionally long-lived (plants more than a century old have been recorded), the Christmas cactus is a very popular houseplant that typically comes into bloom in mid-winter, hence its common name.

Two similar species – Schlumbergera truncata and Schlumbergera × buckleyi – are widely grown, with many different cultivars available that produce flowers in fruity shades of flamingo pink, shocking red and purple as well as white. Unfortunately the Christmas cactus flowers just once a year, but that colourful display does continue over a period of several weeks, while even when out of flower it remains a handsome indoor plant.

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In the wild these species can be found growing in the dappled shade of humid tropical rainforests, which gives you a very good clue as to the kind of growing conditions they need. To ensure a really good display next winter, your plant needs a period of enforced rest from January-March to recover its energies, and then another in autumn (mid-September-November), in preparation for its next showy display of those winter blooms. During both of these periods of rest, Christmas cacti need minimal watering, as well as slightly cooler temperatures (12-15 degrees) than they do when in active growth or bloom (18-20 degrees).

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Many people like to put their plants outdoors in summer in a sheltered spot out of direct sunshine, which helps to “ripen” any new growth in preparation for the formation of flower buds later in the year. Just make sure to choose a spot where the plant’s trailing, fleshy, evergreen stems are safe from slugs and snails (a garden table is a good idea) and to take it back indoors in early autumn before the first frosts. A fortnightly liquid feed from April-September will also help to boost growth, promote the formation of plenty of flower buds and keep your plant healthy and happy.

Christmas cacti are quite easy to propagate from cuttings taken from the plant in late spring/early summer. To do this, gently snap or cut some segments off the ends of the trailing stems and leave them somewhere warm and dry for a day or two to callous over. Then gently bury the base of these segments very shallowly in a small pot filled with a free-draining compost (add some coarse horticultural grit or vermiculite), placing them at intervals around the edge of the pot. Cover the latter with an upturned clear freezer bag sealed with an elastic band and then place the pot somewhere warm and dry (18-24 degrees) but out of direct sunshine. An electric propagator, if you have one, will help speed up the rooting process which typically takes four to 12 weeks. Once new roots start to push their way towards the base of the pot, it’s time to pot those baby plants into their own individual small pots filled with a good-quality, free-draining soil-based compost leavened with plenty of horticultural grit and a little leaf-mould if you have it.

Lastly, bear in mind that Christmas cacti don’t like a sodden compost but they do like plenty of humidity. So it’s a always good idea to place plants on shallow saucers filled with damp pebble or horticultural grit.

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