Scored for a moth orchid at 22 °C and 50% humidity, an east sill at an estimated 6,500 lux comes back 98 out of 100, and a shelf two metres into the room scores the same. The light runs out between 2.5 and 3 m back, where the score drops from 97 to 68. What pulls the sill down is dry air: at 30% humidity, light unchanged, it reads 65.
Read on 14 October 2026, the top results for this search agree about the window and little else. The Philadelphia Inquirer, drawing on Longwood Gardens’ Greg Griffis, files east under “best bet”: morning sun to flower on without burning. Chicago Botanic Garden ranks east alongside south and says to keep the leaves off the pane. Gardening Know How counts hours, about three of sun for a moth orchid, and allows that even an east window may want a curtain. A PBS segment says east is best, then moves a yellowing plant from its east window to a north one.
None says how far back the pot can go, or puts a number on the air. Those two gaps are where the score moves.
Great fit
This plant should be happy in this spot.
Just the right amount of light
Comfortable temperature
Humidity suits it
Airflow suits it
Can a moth orchid sit right on an east sill?
Start with what other people print about an orchid’s light, in the units they print it in and with nobody converting for you.
| Who publishes it | What it says a orchid needs | What the figure is |
|---|---|---|
| growlightmeter.com | 4 – 8 PPFD / DLI | Orchid |
| staugorchidsociety.org | about 10,000 foot-candles | full sun equivalent, stated as too bright for most orchids |
| houseplantjournal.com | 200 FC (40 µmol) foot-candles | minimum indirect light level |
| houseplantjournal.com | 400 FC (80 µmol) foot-candles | good indirect light level |
| houseplantsnook.com | 100–200 foot-candles | chart fc level |
| soltech.com | 40+ PPFD / DLI | minimum fixture PPF to support flowering houseplants |
Yes, and the light gives no reason to move it. The sill estimates at 6,500 lux, inside the band the engine holds for a moth orchid, so the card gives the glass 98/100 with every marker in the middle. That’s the real gap between this window and a south one, where the same orchid is flagged for too much light on the sill and only clears the flag two metres back. Our estimates for east glass don’t reach that level anywhere in the room. The published figures above are about the plant, and none of them knows which window it’s in, so none can settle this on its own.
What the score doesn’t see is a leaf pressed flat against the pane. Glass on a frosty morning, or glass that has had the sun on it for two hours, runs at a different temperature from the room air the card is scored in, and the keep-it-off-the-glass advice is about that contact. The 0.3 m in the worked example already allows for it.
How far back from an east window can an orchid go?
About two and a half metres before anything changes. The same pot, walked back from the glass:
| Distance from the glass | Estimated light | What the light is doing | Verdict |
|---|---|---|---|
| 0.3 m, against the glass | 6,500 lux | Just the right amount of light | Great fit, 98/100 |
| 1 m back | 5,000 lux | Just the right amount of light | Great fit, 98/100 |
| 2 m back | 3,150 lux | Just the right amount of light | Great fit, 98/100 |
| 2.5 m back | 2,500 lux | Just the right amount of light | Great fit, 97/100 |
| 3 m back | 1,984 lux | A little dim, but workable | Worth a try, 68/100 |
| 4 m back | 1,250 lux | A little dim, but workable | Worth a try, 65/100 |
The step sits between 2.5 and 3 m. Over that half metre the estimate falls from 2,500 to 1,984 lux and the score from 97 to 68, and past it the slide is slow, to 65 at four metres. So the habit of keeping an orchid right at the glass is safe but tighter than it needs to be: a table two metres in scores the same 98 as the ledge.
Those lux figures are worked out from the window direction, the distance and a clear day. No meter was involved, and your room will read differently. Where the step falls relative to the glass is the part worth carrying home.
Should an orchid move closer to an east window in winter?
If it lives two metres back, yes. Given a December date at latitude 40, the engine scores the sill and the one-metre shelf just as it does in June, while the two-metre spot slips past the dim edge. For the darkest weeks, keep it within a metre of the glass. By March the two-metre spot is back in range.
Does humidity matter for an orchid in an east window?
More than distance does. Leave the pot on the sill and change only the humidity in the room:
| Humidity at the sill | What the light is doing | What the air is doing | Verdict |
|---|---|---|---|
| 25% | Just the right amount of light | Too dry here | Worth a try, 64/100 |
| 30% | Just the right amount of light | Too dry here | Worth a try, 65/100 |
| 35% | Just the right amount of light | A little dry, but workable | Good fit, 87/100 |
| 40% | Just the right amount of light | A little dry, but workable | Great fit, 91/100 |
| 50% | Just the right amount of light | Humidity suits it | Great fit, 98/100 |
| 60% | Just the right amount of light | Humidity suits it | Great fit, 99/100 |
The light column never moves. The verdict does: 99 at 60%, 98 at 50%, and then most of the fall packed into five points, from 87 at 35% to 65 at 30%. That edge lands where a lot of homes sit in winter. The humidity guide quotes two university sources putting heated homes below 30 per cent through the heating season.
This is where the results talk past each other. Griffis tells the Inquirer that orchids grow fine without extra humidity. The American Orchid Society’s culture sheet asks for 50 to 80 per cent. At 40% the sill still scores 91, so a room at 40 bears him out. At 30% it scores 65, and the society’s range is the one to follow. The engine lands on the same line: the air column first reads “Humidity suits it” at 50%, where their range begins.
If a radiator sits under the window, the pot is sitting in its rising air. The radiator page separates the two things heating does to the air above it, and the one that costs a plant points is the lost humidity, not the warmth.
Should an orchid go in the bathroom instead?
Only if the bathroom has real window light and air that moves. A shower supplies the one thing the humidity table says an east sill can run short of. The bathroom page scores a moth orchid on a shelf at 78% humidity and still finds it flagged, on airflow. The society’s sheet wants air always moving around the plant, and a shut bathroom between showers rarely has it.
Winter is when both of this page’s problems arrive together. The short days pull the pot toward the glass, and the heating dries the room around it. For most homes the simpler fix is the east sill with the air taken care of: a humidifier through the heating months, and some air moving past the leaves. The east window guide already places this orchid on the sill in the morning beam, with African violets and hoyas, and these numbers agree. To score your own sill against your city’s weather instead of a clear day, the spot checker is free.
Published October 14, 2026
