If you want to make a Christmas cactus flower for the holidays, this quick trick will help you persuade your plant to deliver its dramatic magenta blooms right on time. With beautiful pendant blooms that look like a flower within a flower, each with an exotic pink pistil reaching out far beyond the petals, a full-blooming Christmas cactus is a festive treat not to be missed.

Christmas cacti can seem like fickle flowerers because they’re extremely sensitive to their environment. But this hack has them faithfully flowering every Christmas, for years to come – and these are long-lived plants so you could be enjoying festive flowers for the next half-century!

Part of the Weekend Wins series, persuading a Christmas cactus to flower for the holidays is one of those easy jobs that brings a big reward, and guess what? All you need is a cardboard box.

How to Trick Your Christmas Cactus Into Flowering on Time

1. Understand the Blooming Trigger

Schlumbergera is pretty clever because it’s able to track night-length changes to make sure it doesn’t waste energy flowering at the wrong time, thanks to a light-sensitive protein called phytochrome. When the plant is getting lots of light during longer days, the plant grows green segments. However, when the day-night balance switches and the plant receives 12-14 hours of darkness, it stops producing those segments and grows flower buds instead.

The problem comes when we grow Christmas cacti as houseplants, because artificial light interrupts this biological clock. And there doesn’t need to be much light to affect the blooming process: just turning on the TV or a table lamp can trigger that phytochrome to fire up. So, the simple secret to getting beautiful blooms for the holidays is to plunge your plant into darkness for 12-14 hours a day – and yes, that’s where the cardboard box comes in.

2. Prep the Container

Your Christmas cactus needs to be in total darkness for this trick to work, because it’s so ultra-sensitive to light. While some folk use a black trash bag to cover their plant, it’s far better to use a breathable material sufficiently rigid that it won’t touch the stems. A strong cardboard box works well, or I use black fabric grow-bag planters such as these fabric pots from Amazon,as my black-out shrouds.

Check the container is lightproof by upturning the container over a torch in a dark room. You’ll likely need to run over some corners of a cardboard box with duct tape such as Gorilla Tape, available from Walmart.

3. Work Out Timings

It takes 6-8 weeks of long dark nights to trigger flowering. Each Christmas cactus bloom lasts around 5-7 days, with multiple buds that open in succession meaning a plant stays in bloom for 4-6 weeks. That gives you great odds for flowers on Christmas day by beginning the dark treatments around October 15. But, depending on your holiday plans, you may want to shift this date forwards or backwards if you'd like flowering to peak a little before or after the holiday week.

4. Start the Dark Treatment

Every night, pop the box over the plant at around 6pm and remove it at 8am, being careful not to knock the stems. Setting a couple of recurring alarms on your phone as reminders is a smart move. Cut back on watering as a little drought stress is going to help trigger those blooms. While you’d normally water your Christmas cactus when the top inch of soil feels dry, now leave the top 2-3 inches of soil to dry out before watering sparsely. A moisture meter such as this long-probe soil meter from Amazon takes out any guesswork.

5. Restore Light Once Buds Appear

After 6-8 weeks, you’ll spot tiny flower buds forming on the stem tips, which is your cue to end the dark treatment and resume watering your Christmas cactus to keep the soil evenly moist.

Move the Christmas cactus to a spot that’s bright with indirect sunlight (so sunbeams don’t directly hit its stems), with a temperature that stays between 60°F to 70°F. It's easy to check the right temperature with a cheap indoor thermometer such as this from Amazon. If that doesn't fit with your holiday decor plans then a basic dimmable grow light such as this from Walmart will keep your plant happy in lower-light conditions.

Make sure this is the spot you want your cactus to sit over Christmas. These plants are so sensitive to light that moving the pot once all those buds have plumped up – and even turning the pot around so the plant receives light from a slightly different direction – can trigger all those buds to drop.

6. Gift Your Cactus a Pebble Tray

An early Christmas present of a shallow pebble tray at this point will increase the humidity around your plant, mimicking the humid environment of its native Brazilian rainforest canopy. In turn, your Christmas cactus will hold on to its buds better, and the flowers will last for longer. Stand the pot on the pebble tray, and keep topped up with water. It’s vital that the pot base sits on the pebbles and not in the water, so the roots don’t rot. You’re simply using the water to humidify the air as it evaporates.

A Bonsai pebble tray such as this from Lowe’s is ideal, or make your own with a plant saucer and pea gravel pebbles such as this Landscape Rock from The Home Depot.

And that’s it! Take advantage of this simple trick and you should not only have Christmas cactus flowers for the holidays, but a very happy and healthy plant. Now all you need to do is pot up some hyacinth bulbs for festive flowers and you're all set!

More Weekend Wins

This feature is part of the Weekend Wins series, packed with quick and easy 10-minute tasks and gardening tips and tricks that bring a big reward.