Holiday cactus bloom planner
Christmas cactus not blooming?
It is almost always too warm, or getting light at night. Holiday cacti set flower buds after about 6 weeks of long, unbroken nights or cool nights near 13°C (55°F), and nights above 18°C (65°F), lamps or street lights after dark stop them (University of Minnesota Extension, Clemson). The planner below works backwards from the day you want flowers.
Bloom plan
Christmas cactus in flower for Friday 25 December 2026
Dates are worked out from the target you pick.
Start long nights by
Christmas and Thanksgiving cacti bloom after about 6 weeks of short days (University of Minnesota Extension, Penn State).
Every night give it 14 hours of complete, unbroken darkness, from 6 p.m. to 8 a.m. (18:00 to 08:00): a spare room with the lights off, a cupboard, or a box over the plant. As little as 2 hours of light breaks the night (Clemson, Illinois), and street lights, car lights and lamps count. Keep nights at 13 to 18°C (55 to 65°F) and days at 18 to 21°C (65 to 70°F) (University of Minnesota Extension).
Buds should show between and
Clemson says buds are normally visible 3 to 4 weeks after long nights begin. Once buds have set, night length no longer matters (Illinois). If it is going to a warmer room, move it as soon as the buds appear (University of Minnesota Extension), then leave it in place, and keep the compost evenly moist (Clemson).
Target bloom:
Keep the routine going until buds are well formed; Clemson says at least 6 continuous weeks, which brings you to your target date. Bud drop comes from draughts, sudden changes in temperature or light, too many buds, and compost that is too wet or too dry (University of Minnesota Extension, Clemson, Illinois).
Sources: UMN Extension, holiday cacti; Clemson HGIC, holiday cacti; Penn State, holiday cacti; Illinois Extension, holiday cacti
Why a Christmas cactus does not bloom
Holiday cacti are short-day plants: they form flower buds when nights are long and cool, as they are in autumn. University of Minnesota Extension lists three reasons one stays green.
- The room is too warm. Blooming is unlikely with nights above 18°C (65°F) (University of Minnesota Extension), and Iowa State says temperatures above 21°C (70°F) prevent flowering even with short days. The RHS says flowers fail when the temperature never falls below 18°C (65°F).
- Light at night. Lamps, street lights or car headlights during the dark period can stop buds forming, and as little as 2 hours of light breaks the treatment (Clemson). Indoor lighting counts too, so a plant in a lived-in sitting room may never get a truly dark night.
- Too few long nights, or too little feed. Minnesota’s minimum is 12 hours of total darkness a night, and it suggests feeding monthly at half strength from June to August.
What the extension services say
The sources agree on the idea and differ a little on the numbers, mostly because a cooler room needs fewer hours of darkness.
| Source | Darkness each night | How long | Night temperature |
|---|---|---|---|
| University of Minnesota Extension | At least 12 hours | About 6 weeks | 16–18°C (60–65°F); at 13°C (55°F) bloom in 5–6 weeks, sometimes whatever the day length |
| Clemson HGIC | 14 hours or more | At least 6 weeks from mid-September; buds show in 3–4 weeks | 10–15°C (50–59°F) sets buds regardless of day length |
| Penn State Extension | 12–14 hours | 6 weeks (Easter cactus 8–12) | 13–18°C (55–65°F) |
| NC State Extension | At least 13 hours | Mid-September to mid-November | 13–18°C (55–65°F) |
| Iowa State Extension | 14–16 hours (some cultivars 12) | Not stated | Above 21°C (70°F) prevents flowering |
The planner defaults to 14 hours, which meets every minimum except the top of Iowa State’s range, and counts back 6 weeks for Christmas and Thanksgiving cacti and 8 to 12 weeks for the Easter cactus. Once buds have set, night length no longer matters (Illinois Extension).
How to give it long nights
Put it in a spare room, a cupboard or under a box from early evening to morning, every night without a break, and back in bright light by day. Keep nights at 13 to 18°C (55 to 65°F) and days at 18 to 21°C (65 to 70°F) (University of Minnesota Extension). A cool porch or unheated room that stays near 13°C (55°F) can do the job without the box, but not at 10°C (50°F) or below, when buds may drop (Clemson, Illinois). The RHS also suggests watering less during the autumn cool spell; once buds form, Clemson says to keep the compost evenly moist.
Why the buds drop
Bud drop is the other common complaint. Minnesota names draughts and sudden changes in temperature or humidity; Clemson adds too many buds and compost drying out; Iowa State warns that moving the plant before the flowers open can cause it; and the RHS mentions cold on the journey home from the shop. If it has to go to a warmer room, move it as soon as the buds appear, then leave it in place.
Christmas, Thanksgiving or Easter cactus?
Clemson notes that the Thanksgiving cactus is the one most often for sale over the winter holidays, and that it normally flowers about a month before the Christmas cactus. The stem segments tell them apart.
The Thanksgiving cactus (Schlumbergera truncata) has 2 to 4 pointed teeth on each segment and yellow pollen; Iowa State gives its season as mid-November to late December. The true Christmas cactus (S. × buckleyi) has rounded, scalloped segments, purplish-brown pollen and flowers that hang down. The Easter cactus has smoother segments with brownish bristles at the tips and star-shaped flowers from March to May (Iowa State, Illinois Extension).
Worked examples
- Christmas cactus for Christmas Day, Friday 25 December 2026: start long nights by Friday 13 November 2026. Buds should show between 4 and 11 December.
- Thanksgiving cactus for US Thanksgiving, Thursday 26 November 2026 (date from the US Office of Personnel Management): start by Thursday 15 October 2026.
- Easter cactus for Easter Sunday, 28 March 2027: start between Sunday 3 January and Sunday 31 January 2027.
If the start date has already passed, start now: the plan still works, the flowers just come later.
The rest of the year
After flowering, water less until spring (University of Minnesota Extension). Holiday cacti bloom best somewhat pot-bound, so repot only about every three years, in spring (Minnesota, Clemson). They can summer outdoors in part shade with 3 to 6 hours of sun, and should come in once autumn nights reach the low 50s °F, about 10 to 12°C (Minnesota, Illinois).
General information from the extension pages listed below, not professional advice. The ASPCA lists the Christmas cactus as non-toxic to cats, dogs and horses: see plants toxic to cats and dogs.
Frequently asked questions
Why won’t my Christmas cactus bloom?
Usually it is too warm at night or gets light after dark. It needs about 6 weeks of long, unbroken nights at 13 to 18°C (55 to 65°F), or cool nights near 13°C (55°F), to set buds.
How many hours of darkness does a Christmas cactus need?
Sources range from at least 12 hours (University of Minnesota Extension) to 14 hours or more (Clemson). Fourteen hours, for example 6 p.m. to 8 a.m., satisfies most of them.
When should I start for flowers at Christmas?
About 6 weeks before: by Friday 13 November 2026 for Christmas Day 2026. Clemson starts its long nights as early as mid-September and keeps them going for at least 6 weeks.
Why is my Christmas cactus dropping its buds?
Draughts, sudden changes in temperature or light, moving it before the flowers open, too many buds, or compost that is too wet or too dry (University of Minnesota Extension, Clemson, Iowa State).
Is a Christmas cactus toxic to cats?
The ASPCA lists the Christmas cactus as non-toxic to cats, dogs and horses. It has no separate page for the Thanksgiving cactus.
Sources
All opened and checked on 3 November 2026. Temperatures in °C are converted from the sources’ °F figures (the RHS gives °C).
- Holiday cacti. University of Minnesota Extension, reviewed 2026.
- Thanksgiving & Christmas Cacti. Clemson Cooperative Extension, Home & Garden Information Center, updated 29 November 2018.
- Bring on the Blooms with Holiday Cacti. Penn State Extension Master Gardener Program, 2 December 2024.
- Schlumbergera (Plant Toolbox). NC State Extension.
- Schlumbergera truncata (Plant Toolbox). NC State Extension.
- All About Holiday Cacti. Iowa State University Extension and Outreach, reviewed December 2025.
- How to identify and care for holiday cacti and get them to rebloom. University of Illinois Extension, 9 December 2022.
- How to grow Christmas cactus. Royal Horticultural Society.
- Federal Holidays. U.S. Office of Personnel Management.