A Christmas cactus that grows happily all year and then never flowers is almost always living in a room that's too warm and too brightly lit in the evenings. It isn't short of food and it isn't sulking. Buds form in response to a cool spell and long, uninterrupted nights in autumn, and a cosy sitting room with the lamps on until eleven gives it neither. The fix is free, and the time to start is mid-September.
01At a glance
- When: from mid-September until you see buds. The RHS expects flowers between late November and late January.
- Cool: a distinct drop to around 12–15°C. A spare bedroom or cool landing is ideal.
- Dark: long, unbroken nights. Evening lamplight, even a little, can stop buds forming.
- Steady once budded: sudden swings in temperature or light, overwatering and drying out all make buds drop.
- Not a desert cactus: it comes from forest, not sand, and needs more water than a spiny cactus.
02How to set the buds
- Move it somewhere cool in mid-September. The RHS suggests 12–15°C until buds appear. The exact number isn't critical. What matters is a clear drop from normal room warmth. If the room never falls below about 18°C, the RHS warns, it may not flower at all.
- Give it proper nights. Clemson University's extension service says these plants need 14 hours or more of continuous darkness a day, for at least six weeks. Pick a room nobody uses after dark, away from lamps, the TV and streetlights through the window. Clemson notes that even a couple of hours of light in the middle of the night can stop buds setting.
- Water less, but don't let it dry right out. During this cool rest the RHS lets the top few centimetres of compost dry between waterings, without the pot going bone dry.
- Stop feeding. The RHS feeds from April to the end of September only. Clemson also stops in late summer to encourage buds.
- Wait. Clemson says buds usually appear three to four weeks into the long-night treatment. Once they're set, day length no longer matters.
03Once you can see buds
This is where most plants lose their flowers. When the first buds appear, the RHS moves the plant back to its usual spot at about 18–20°C and resumes regular watering until the flowers fade. Make that one move gently, then leave it alone. Don't keep turning it to the light or carrying it about to show people.
What actually knocks buds off, according to the RHS and Clemson:
- Fluctuating temperatures, such as hot by day near a radiator and cold by night against the glass.
- Sudden changes in light or position.
- The compost drying out, or the opposite, overwatering.
- Cold draughts, including on the way home from the shop.
Clemson also notes that a plant carrying a huge number of buds may shed a few. That's the plant trimming its own load, not a sign you've failed.
04Christmas or Thanksgiving cactus?
There are two common types, and they're cared for the same way. Look at the edges of the flat stem segments:
- Thanksgiving cactus (Schlumbergera truncata): two to four pointed, saw-toothed projections along each segment. Clemson says it usually flowers about a month earlier, and its flowers have yellow anthers.
- Christmas cactus (Schlumbergera × buckleyi): more rounded, scalloped edges, and purplish-brown anthers.
If yours flowers in November rather than December, it may simply be a Thanksgiving type doing exactly what it should.
05It's a forest plant, so water it like one
Schlumbergera comes from tropical rainforest, not desert. The RHS waters it regularly from April to September, keeping the compost moist but not waterlogged, and waters again once buds form, right through flowering, rather than keeping it dry all winter like a desert cactus. Our Christmas cactus profile has the full care details. Never leave it standing in a saucer of water.
After flowering, the RHS gives it a second cool, drier rest from late January to late March. In summer it enjoys a sheltered, shady spot outdoors, which helps ripen the stems for next year's flowers. Keep it out of full sun and watch for slugs. Bring it in before the nights turn cold.
06Mistakes that cost you flowers
- Leaving it in the warm sitting room all autumn. The most common reason it won't flower.
- Switching on a lamp beside it every evening. Long nights only count if they're unbroken.
- Moving it again and again once it's in bud.
- Feeding it in autumn to "help" it flower.
- Letting it go bone dry, as you would a desert cactus.
How we checked this
Every care and safety claim on this page is verified against horticultural and veterinary sources.
Sources: RHS — Christmas cactus: growing guide · Clemson Cooperative Extension HGIC — Thanksgiving & Christmas cacti
Checked 8 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.