Put a Christmas cactus against north glass and it scores 99 out of 100, at 22 °C and 50% humidity, on a clear-day estimate of 3,640 lux. At latitude 40 that light stays inside this plant’s band on every day of the year. What changes is the strip behind it: on a clear day the great fit reaches 1.7 metres from the glass, but only the first 55 centimetres keep it all year.
Read on 22 October 2026, the answer box at the top of Google’s results calls a north window “a great spot” for this plant. Its case: a tropical plant that wants bright, indirect light and burns easily in harsh sun gets gentle, canopy-like light there, with no sheer curtain needed. It adds that north rooms run cooler, which it counts toward setting winter buds, and warns that a room too dim may flower less than an east one or need a lamp. It cites r/cactus, two YouTube channels and an Instagram account. Under it come Reddit threads, a video about cacti in north windows, UF/IFAS, cactusoutlet.com, MSU Extension and cactiguide.com.
Great fit
This plant should be happy in this spot.
Just the right amount of light
Comfortable temperature
Humidity suits it
Airflow suits it
Is a north window bright enough for a Christmas cactus?
At the glass, yes. Here is what the care pages put in numbers for this plant, each in its source’s own unit:
| Who publishes it | What it says a Christmas cactus needs | What the figure is |
|---|---|---|
| gardeningsolutions.ifas.ufl.edu | within six feet | How close to place it to a south-, east- or west-facing window |
| gardeningsolutions.ifas.ufl.edu | at least twelve hours of darkness | What it typically needs in order to flower |
| livelyroot.com | 4-6 hours of morning sunlight | Daily morning sun, given so the plant avoids prolonged exposure to harsh light |
| livelyroot.com | 13+ hours of darkness daily | With cooler temperatures, to encourage flowering |
| libanswers.nybg.org | at least two hours of winter sun | NYBG's light preference for Schlumbergera bridgesii, together with very bright light conditions |
| libanswers.nybg.org | 13 hours of uninterrupted darkness | What produces buds when the temperature is between 55° and 70°F |
| site.extension.uga.edu | around 13 to 16 hours each night | Total darkness for the best flowering; UGA Extension county article, December 2022 |
| site.extension.uga.edu | Fourteen hours or more of continuous darkness each day | Required before flower bud set, in the same article |
| extension.arizona.edu | at least 15 hours long | How long the nights must be for Thanksgiving and Christmas cacti to bloom; University of Arizona Cooperative Extension, Yavapai County, July 2024 |
NYBG and Lively Root both ask for sun that north glass won’t deliver: at least two hours of winter sun for NYBG, four to six hours of morning sun for Lively Root. A north window sees open sky and almost never the sun itself. The RHS pulls the other way, saying these cacti dislike full sun. Our care data asks for less than NYBG does. It files this plant under bright, indirect light, and the sill’s 3,640 lux lands inside that band, which is how the card gets to 99. Nothing at this window reads too bright for it either, so the box’s no-curtain advice holds.
UF/IFAS stays quiet on north. Its six feet is offered for south, east and west windows only, and at north glass six feet lands just past the step in the next table. The missing sun has one upside: no afternoon beam heats the pane, and heat is what flags this plant on a west sill once the air passes 27 °C.
How deep into a north room can a Christmas cactus go?
Leave the calendar out and the answer is 1.7 metres, about five and a half feet. One pot, carried back from the glass:
| Distance from the glass | Estimated light | What the light is doing | Verdict |
|---|---|---|---|
| 0.3 m, against the glass | 3,640 lux | Just the right amount of light | Great fit, 99/100 |
| 1 m back | 2,800 lux | Just the right amount of light | Great fit, 98/100 |
| 1.7 m back | 2,026 lux | Just the right amount of light | Great fit, 97/100 |
| 1.75 m back | 1,980 lux | A little dim, but workable | Worth a try, 68/100 |
| 3 m back | 1,111 lux | A little dim, but workable | Worth a try, 64/100 |
| 4.3 m back | 609 lux | A little dim, but workable | Worth a try, 62/100 |
| 4.35 m back | 595 lux | Too dim here | Not the best fit right now, 47/100 |
The step falls between 1.7 and 1.75 metres, where the estimate dips from 2,026 to 1,980 lux and the score from 97 to 68. Past it the slope is gentle. Worth a try holds to 4.3 metres, and only from 4.35, at 595 lux, does the light read too dim and the verdict drop to not the best fit. On our scale, the dim room the box warns about begins at that first step. The too-dim row sits about fourteen feet from the glass.
Every lux figure here is worked out from the window’s direction, the pot’s distance, a clear sky and, for the next table, the date and latitude; none came off a meter.
A Thanksgiving cactus, Schlumbergera truncata, comes out the same as this plant in every table on the page.
How close to a north window should a Christmas cactus be in winter?
Closer than the distance table suggests, and the further back it sits, the earlier it needs to move. On the sill nothing changes at latitude 40. A metre back, the light slips out of the band right through the holidays. That metre-back spot, month by month:
| The month | Estimated light | What the light is doing | Verdict |
|---|---|---|---|
| September | 2,792 lux | Just the right amount of light | Great fit, 98/100 |
| October | 2,263 lux | Just the right amount of light | Great fit, 97/100 |
| November | 1,803 lux | A little dim, but workable | Worth a try, 68/100 |
| December | 1,634 lux | A little dim, but workable | Worth a try, 67/100 |
| January | 1,820 lux | A little dim, but workable | Worth a try, 68/100 |
| February | 2,289 lux | Just the right amount of light | Great fit, 98/100 |
| March | 2,783 lux | Just the right amount of light | Great fit, 98/100 |
Scored day by day, the pot a metre back loses its great fit on 7 November and gets it back on 4 February. Christmas sits in the middle of that stretch. At 1.25 metres, about four feet, the great fit goes even sooner, on 23 October. To keep it every day of the year the pot has to stay within 55 centimetres of the pane. By the same test an east window allows 1.45 metres and a west one 1.85.
Further north the sill has a limit of its own. Around Boston, at 42 degrees, it still holds a great fit every day; a little beyond that it starts slipping for a few days at the solstice. At 51.5 degrees, London’s latitude, the sill reads worth a try from 13 November to 28 January, while an east or a west sill there keeps a great fit all winter. That gap is where the box’s lamp comes in. Our estimate counts daylight through the window and nothing else, so it can’t say how much one helps.
Does a cool north room help a Christmas cactus bloom?
The score can’t say. It reads comfort and knows nothing about day length or flower buds, and it counts cool air as a cost: under 13 °C this sill is not the best fit, from 13 °C it’s worth a try, and from 17 °C a great fit again. The east-window page sets that cool end beside the bud-setting nights the care pages ask for, and the cold-drafts guide makes this plant the exception among succulents comfortable at around 10 °C.
A north room changes the picture after the buds show, when the RHS wants the plant back at its usual 18 to 20 °C. On a sill at latitude 40 that warmth restores the great fit. A metre back in December it can’t, because the light alone keeps the pot at worth a try.
What can make a north sill darker than this?
Anything that takes sky off the pane, a building close across the street or a balcony overhead, is missing from these numbers, and in midwinter this sill has little light to spare. The north window guide scores what else holds at this glass, and the free spot checker runs your own window with your local weather.
Published October 22, 2026
