How to get a Christmas cactus to flower: long nights, a cool room and no bud drop

A Christmas cactus that never flowers is usually getting too much light in the evening or too much warmth in autumn. It sets buds when nights are long and a little cooler. Below, one example runs from a cactus with no buds in November to a plant in flower, with a drawing for every step.

Our example: Amira's cactus with no buds

Every step below follows one story, and each drawing shows that exact moment. On 1 November, Amira's Christmas cactus has no buds. It lives on a shelf in her warm living room, where the lamp is on every evening. She moves it to the cool spare room, waits for buds, then brings it back.

Part 1: Check which cactus you have

1. Look at the edges of the stem segments.

   

   In our story: Amira looks closely. Her plant's segments have smooth, rounded edges, so it's a Christmas cactus.

   Thanksgiving cactus has 2 to 4 pointed, saw-like teeth on each edge of its flat segments; Christmas cactus has rounder edges (Clemson Extension). Thanksgiving cactus usually flowers about a month earlier, so if yours has teeth, start sooner. Both need the same long nights.

Part 2: Get it to set buds

1. Move it somewhere cool and bright.

   

   In our story: Amira puts the cactus on the windowsill of the spare room, where the heating is turned low.

   The RHS suggests a cooler spell of about 12 to 15 °C from mid-September until buds appear; exact temperatures aren't critical, but there should be a clear drop. Clemson gives 15 to 20 °C by day, and says cool nights of 10 to 15 °C help buds set. Keep it in bright light but out of full sun (RHS), and above 10 °C.

2. Give it long, dark nights.

   

   In our story: Nobody switches the spare room light on in the evening, and Amira draws the curtain so the street light stays out.

   It needs 14 hours or more of unbroken darkness every night for at least 6 weeks (Clemson Extension). Even a couple of hours of light can stop buds forming, including street lights, car headlights and lamps (Clemson). The RHS also warns that artificial light after dark can stop flowering. Clemson says to start around mid-September; starting in November, flowers may come after Christmas (our estimate).

3. Water a little less.

   

   In our story: Amira only waters when the top of the compost feels dry.

   During this cool spell, water less often (RHS). Let the top few centimetres dry between waterings, but never let the compost dry out completely (RHS).

4. Watch for buds at the tips.

   

   In our story: In mid-December, small pink buds appear at the ends of the segments.

   When buds appear, the cool spell has done its job (RHS).

Part 3: Keep the buds and enjoy the flowers

1. Bring it back, away from heaters and draughts.

   

   In our story: Amira carries it back to the living room and sets it on a side table, away from the radiator and the front door.

   Once buds appear, move it back to its usual warmer spot, about 18 to 20 °C (RHS). Buds drop when temperatures swing, or in cold, draughty spots (RHS), or with sudden changes in light or temperature (Clemson). Once it's in bud, choose its place and leave it there.

2. Water evenly and empty the saucer.

   

   In our story: She waters whenever the top feels dry, and tips away what drains into the saucer.

   Once buds appear, go back to normal watering until the flowers fade, without overwatering (RHS). Keep the compost evenly moist and never leave water standing in the saucer (Clemson).

3. Enjoy the flowers.

   

   In our story: By New Year, the cactus is covered in pink flowers.

   At about 20 °C the flowers can last 7 to 8 weeks (Clemson Extension).

Part 4: After flowering

1. Give it a cool, drier rest.

   

   In our story: At the end of January, Amira moves the cactus back to the spare room until spring.

   The RHS suggests a cooler, drier rest from late January to late March, then normal watering from spring until mid-September. In summer it can go outside in a warm, sheltered, shady spot, and come in before the nights turn cold (RHS).

If the buds drop

1. Don't put it by a radiator or an open door.

   

   What if Amira had put it above the radiator? Warm days and cooler nights would make the buds fall before they open.

   Temperatures that swing between too hot by day and too cold by night are the usual cause of bud drop (RHS). Cold draughts, including on the way home from the shop, and overwatering can cause it too (RHS).

If something goes wrong

Related: How to repot a houseplant · How to tell if a houseplant needs water.