A Burgundy rubber plant on an unshaded south sill gets about 13,000 lux on a clear day, and at 22 °C with 50% humidity we score that spot 100 out of 100. A metre back it’s still 100. Two metres back, 98. Half a metre further, at 5,000 lux, it drops to 67. That step is where this window goes wrong.
Read on 14 October 2026, the top results can’t agree where the pot goes. Easyplant puts it on the windowsill or close to a south window. In a 2022 r/houseplants thread, one grower keeps theirs on a bench by the glass and another keeps two ficus about three feet back. The Spruce says several feet from the window. Spider Farmer says not directly in front of one without a sheer curtain, and Joy Us Garden warns the leaves can burn against hot glass, “especially in summer.”
On our scoring, everything from that bench to six feet back lands in this plant’s top band. The summer warnings are really about heat, and our numbers find it in the air on the sill.
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 south sill too much sun for a rubber plant?
Published light figures for a rubber plant run from under a hundred foot-candles to several thousand. Here they are as each source prints them:
| Who publishes it | What it says a rubber plant needs | What the figure is |
|---|---|---|
| theplantrunner.com | 800–2,000+ lux | Standard foliage plants (pothos, Philodendron, Monstera deliciosa …) — a general band, not a single-species figure |
| bbg.org | as little as 250 foot-candles | India Rubber Tree (Ficus elastica) |
| bbg.org | 4,000 to 8,000 foot-candles | India Rubber Tree (Ficus elastica) |
| extension.arizona.edu | 75–150 foot-candles | listed under the heading "Medium Light (75–150 fc)" |
| houseplantjournal.com | 400 FC (80 µmol) foot-candles | minimum indirect light level |
| houseplantjournal.com | 800 FC (160 µmol) foot-candles | good indirect light level |
| houseplantsnook.com | 200–400 foot-candles | chart fc level |
No. The card above has the sill at 100/100 with all four markers in band, the light at 13,000 lux among them. Our care data files this plant with the high-light group, whose band reaches past anything our estimates put on a south sill. Even in June at latitude 40 degrees, when the sill estimate peaks for the year, the light doesn’t flag.
Spider Farmer’s alternative, a north or east window, is where a reader gives something up. A north sill only gets this plant to worth a try. East glass does give it a great fit, but only up against the pane: a metre back from an east window the light is already flagged.
How far back from a south window can a rubber plant go?
About two metres with almost nothing lost on the way, and then the light steps down. Here is one plant walked back from one south window:
| Distance from the glass | Estimated light | What the light is doing | Verdict |
|---|---|---|---|
| 0.3 m, against the glass | 13,000 lux | Just the right amount of light | Great fit, 100/100 |
| 1 m back | 10,000 lux | Just the right amount of light | Great fit, 100/100 |
| 2 m back | 6,300 lux | Just the right amount of light | Great fit, 98/100 |
| 2.5 m back | 5,000 lux | A little dim, but workable | Worth a try, 67/100 |
| 3 m back | 3,969 lux | A little dim, but workable | Worth a try, 66/100 |
| 5 m back | 1,575 lux | Too dim here | Not the best fit right now, 47/100 |
The drop sits between the two-metre row and the next one. The estimate falls from 6,300 to 5,000 lux, the light column turns from just right to a little dim, and the score goes from 98 to 67. Probing in between puts the step just past two metres. After that it sags slowly, 66 at three metres, until about five metres back the light runs out and the verdict is 47.
Now hold the published distances against it. Three feet is about a metre, which is the 100 row. Several feet works here if it means six, and stops working by eight, because eight feet is already past the step. The Spruce’s sentence covers west windows too, and at a west window two metres puts this plant on the flagged side.
Those lux figures are estimates from the window’s direction, the distance and a clear sky, not meter readings. An eave or a tree outside shifts every row, and the step moves with them.
Does hot glass in summer hurt a rubber plant?
Hot air can. Keep the pot on the sill, leave the light at 13,000 lux, and change only the air temperature:
| Air temperature at the sill | Verdict |
|---|---|
| 18 °C | Worth a try, 68/100 |
| 19 °C | Great fit, 99/100 |
| 24 °C | Great fit, 100/100 |
| 28 °C | Great fit, 99/100 |
| 29 °C | Worth a try, 68/100 |
| 33 °C | Not the best fit right now, 48/100 |
From 19 to 28 °C the sill holds the top band. At 29 °C it falls to 68 and at 33 °C to 48, with the light the same on every row. Each edge is a single degree wide. The warm one is easy to cross without noticing, because a closed south window in full sun can heat the air right behind it past whatever the thermostat across the room says.
So Joy Us Garden’s summer warning is aimed at something real. Our score reads the air around the plant, though, and a leaf lying flat on sunlit glass is a case it doesn’t cover. A hand’s width between the leaves and the pane costs nothing.
A south window makes the hot weeks easy to handle. Pull the pot a metre or two in and the first table says it keeps a great fit on light. Whether the air there is cooler depends on your room, so check rather than assume. A sheer curtain is the other usual answer, and the fiddle leaf fig page for this window covers what one changes on south glass.
Should a rubber plant move with the seasons?
For heat, yes. For light we don’t score a south window month by month: through vertical south glass the low winter sun reaches further into the room than the high summer one, and our seasonal estimate doesn’t yet account for which way the glass faces.
Put the clear-day distances next to the heat table and a routine falls out anyway. Through the hot months the pot can stand a metre or two in, away from the warm air at the glass, and give up almost nothing. Only a sill that sinks below 19 °C on winter nights is a reason to keep it a little in. A fiddle leaf fig at a west window is a case where the calendar does move the answer.
Is south the best window for a rubber plant?
For room to work in, yes. The strip of floor where this plant scores a great fit runs about two metres deep from south glass, about one metre from west glass, and only about half a metre from east glass. A north window never gets it into that band on our scoring.
All of it assumes a clean south window and a clear day. A balcony overhead or a building across the street takes light off every row and pulls the step toward the glass. The south window guide shows how quickly light falls away across a south room, and the free spot checker scores the window you actually have.
Published October 14, 2026
