I've had a Phalaenopsis for almost a year and a half, and I keep it in my bedroom near the window but I haven't seen a single bud. I water it when the substrate is dry, and I use demineralized water. The leaves are green and look nice, so it's not dying, but I can't figure out why it won't give me the flowers it promised.
The nighttime cold helps, but that's not everything, because your bedroom might still have too uniform temperatures overall. What's really missing is light: Phalaenopsis need several hours of intense light to develop buds, and a bedroom window often isn't enough, especially if you have curtains or the sun doesn't hit it directly. Try moving it to a brighter spot (like in front of a window that gets sun for a good stretch), and add a real temperature drop - you don't need to overdo it, maybe just keep it a bit cooler at night for a couple of months - but without strong light it's hard for it to flower anyway.
Phalaenopsis orchids need a temperature shock to bloom, and that's probably what yours is missing. In nature, these orchids flower after a cold period (roughly 10-15 degrees at night for a few weeks), which triggers them to produce flowers. If you keep it in your bedroom at a constant, warm temperature, the signal to bloom never comes. Try placing it somewhere cooler during autumn and winter, maybe near a window where it feels the temperature change between day and night. Even just a few degrees' difference can make all the difference.
The other thing that matters a lot is light. "Near the window" in your bedroom doesn't necessarily cut it - it depends on how much sun actually reaches it. Phalaenopsis orchids love bright, diffuse light, ideally 12 to 16 hours a day. If your window faces north or gets shade most of the time, the orchid doesn't accumulate enough energy for buds. Try moving it somewhere brighter, even if it's not in direct scorching sun (that burns the leaves).
Finally, check whether it's been in the same substrate all this time. If the bark or orchid potting mix breaks down after a year, the roots struggle, and a stressed plant won't bloom. Change the substrate every 1-2 years or so. And also: Phalaenopsis orchids appreciate a bit of fertilizer, especially with a phosphorus-rich formula when the right time for flowering comes around. Demineralized water is fine, but without nutrients the plant doesn't have the resources to produce flowers.
I noticed the same thing with my plants at home: when they're too warm all year round, they have no incentive to flower. The person who answered before was right about the cold nights, but I'd add that light is just as important - if your bedroom isn't super bright, it might not be enough to trigger blooming. Try moving it closer to the window (maybe east or west facing where it gets direct light in the morning or afternoon) and if you can handle slightly cooler nights in winter, even better. Often that seasonal change is all it takes to get the plant to produce buds.
How much light is it actually getting in that bedroom? Because light is the main culprit when Phalaenopsis won't bloom - way more than people realize. A north-facing window or one with minimal direct light just isn't enough. These orchids need lots of brightness, even if not scorching sun during the hottest hours. If the room is dark or the window is blocked by curtains, the plant will make leaves but won't have the energy for flowers.
The second point is the temperature shock you've already read about in the other answers - it's true that you need a nighttime drop of at least 5-7 degrees compared to daytime to trigger blooming. But there's a trick most people don't use: keep the plant as cool as possible during winter (even 15-16 degrees at night is fine) and at the same time cut back watering a bit. You don't need total dryness, but the substrate shouldn't stay constantly wet. This combo of cold + slightly drier works as a biological trigger.
Try moving the Phalaenopsis to a spot in your house where it gets at least 3-4 hours of strong indirect light per day. If you have a south, east or west-facing window, that's better. Then when the cold season arrives (November-January where you are), keep it cool at night and slightly reduce your watering schedule. With these two factors together you should see buds within 2-3 months.
Don't assume that cold alone will solve everything, because the real problem is often that orchids indoors are in environments that are too uniform with little direct light 🌿 Phalaenopsis leaves do fine with low lighting, but to flower it needs way more light than what it gets from a bedroom window, especially in winter. Try moving it to a brighter room, maybe a living room facing south or in front of a larger window, and then yes add the temperature shock too (a few weeks with nighttime temperatures around 15-16 degrees between November and December) - light and cold together work the magic, not just one 💡 the combination of these two factors is what your orchid is missing, not just being in the cold.
Try moving it to a spot with more direct light, ideally facing east or west, and see if anything changes over the next two or three months. A bedroom by the window sounds good in theory, but it really depends on which way it faces and how many hours of actual sun it actually gets. If it's north-facing or the window's blocked by thick curtains, the plant might not be getting enough light to trigger flowering. Phalaenopsis aren't shade plants, despite what people often say.
That said, the others are right about the nighttime cold too: without a temperature drop, even with the right light the plant might decide it's not time to flower. Try to give it at least a 5-10 degree difference between day and night if you can. It doesn't have to be dramatic - just a bit cooler at night than during the day. In my place, when I moved an orchid from the heated kitchen (where it sat at the same temperature year-round) to a cooler, brighter window, after a few months it started putting out a flower spike.
Focus on the light first, though. It's the factor people underestimate the most, and often that's exactly what's missing.
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