Your plant is failing, and the thing you’re surest about is that it can’t be light. The room is bright. That certainty is usually the problem. “The room is bright” is a sentence about the window. Your plant lives on a shelf, and the shelf is a different, much darker place than the glass a few steps away.
Worth a try
It can work here with a little care.
A little dim, but workable
Comfortable temperature
Humidity suits it
Airflow suits it
Start with the likeliest cause: the spot is dimmer than it feels
Your eyes adapt so smoothly that a 90-plus-percent drop in light reads as “a little dimmer.” We put a phone down in six places in one bright living room, all six inside the same hour, and the readings ran from 20,000 lux at the glass to 18 lux in the corner; the full six-spot walkthrough is here. The shelf that feels fine can be a small fraction of the window’s light. Before anything else, measure the exact spot: not the room, the pot’s spot. It’s the single most common hidden cause of a slow, mysterious decline.
The word doing the damage is “bright”, and it is worth very little as a number. Four sources put a figure on it and they do not agree with each other, or in one case with themselves.
| Published by | The figure | As written |
|---|---|---|
| extension.illinois.edu | 10,000–12,000 fc | Outdoors: “Outdoors, the amount of sunlight that is cast may be 10,000 to 12,000 foot-candles.” |
| extension.illinois.edu | 300 fc | Indoors, the same page’s top band: “High or Bright Light (300 foot candles)”. |
| extension.arizona.edu | 150–1000 fc | “In general, there are three categories of light intensity for interior plants: high, 150–1000 foot-candles (fc); medium 75–150 fc; and low, 25–75 fc.” |
| extension.arizona.edu | More than eight feet | “Low Light: areas more than eight feet from windows as in the center of a room, a hallway or an inside wall.” |
| extension.msstate.edu | 1,000 fc, then 100 a few feet in | Not a floor but a falloff, from the same source: “The intensity of the light can drop from 1,000 to 100 foot-candles in the distance of only a few feet.” |
| extension.msstate.edu | 1,000 fc and up | “High represents light conditions that are 1,000 or more foot-candles in intensity” — the same page also heads a section “High Light (150 to 1,000 foot-candles)”. |
| extension.msstate.edu | Under 50 fc | “Usually, an intensity of less than 50 foot-candles will not sustain plant life for very long”. |
| open.edu | 100,000 lux | “Sunlight is extremely bright and its illuminance can reach 100 000 lux on the ground.” |
| open.edu | 200–300 lux | “Daylight penetrating windows into a building can provide illuminance levels of around 200–300 lux in typical naturally lit offices for most of the day.” |
Those six readings in the living room were ours, off a meter, and the wider pile behind them is public too: 204 readings at 104 spots over 36 days, where the middle half of the indoor ones still spans 420 to 6,200 lux.
The other half: can it be too much light at all?
The other half of the question comes up just as often, and the advice for it is a list of symptoms: scorched patches, bleached colour, crisp edges. Symptoms are the slow way round. Whether a spot can be too bright at all is decided before any leaf is involved, by which plant is standing in it. Put four of them on one south-facing sill, reading the identical light, and the same 13,000 lux comes back too bright for the cast iron plant, too bright for a golden pothos, just right for a rubber plant and a little dim for an aloe.
That is one reading, at one moment, in one place, and it does not come back as one answer. So “is this too much light” has no answer until you say for what. Plants in the two brighter bands cannot be overdone by an indoor window at all: the first reading that comes back too bright for a plant like the rubber tree is roughly double what the brightest sill in a house delivers, and for a full-sun plant like the aloe it is outdoor daylight. For those, a bright room is never the problem, and a symptom list will send you looking for a cause that is not there.
In one bright room, the same walk goes both ways
This is where a room-level answer stops working. Take the cast iron plant off that sill and walk it into the room:
| Distance from the glass | Estimated light | What the light is doing | Verdict |
|---|---|---|---|
| 0.3 m, against the glass | 13,000 lux | Too bright here | Not the best fit right now, 41/100 |
| 1 m back | 10,000 lux | A bit bright, but workable | Worth a try, 61/100 |
| 2 m back | 6,300 lux | A bit bright, but workable | Worth a try, 65/100 |
| 3 m back | 3,969 lux | Just the right amount of light | Great fit, 94/100 |
| 4 m back | 2,500 lux | Just the right amount of light | Great fit, 94/100 |
Three metres back it stops being a burn risk and becomes a great fit. Note that this ceiling is an indoor one: step through the door and the numbers leave the range a window can reach. Now take the same four steps with the rubber plant, in the same room, on the same afternoon:
| 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 |
| 3 m back | 3,969 lux | A little dim, but workable | Worth a try, 65/100 |
| 4 m back | 2,500 lux | A little dim, but workable | Worth a try, 63/100 |
The walk that rescued the first plant is the walk that starts breaking the second. Both readings are true, they are three metres apart, and no sentence about the room can hold both of them. That is the whole reason the answer here is a spot rather than a room, and why the useful question is not “is my room bright” but “what does the pot’s own place read.”
Then work down the list
- Overwatering that’s really under-lighting. In a dim spot a plant uses water slowly, the soil stays wet, and the roots suffer. But the fix is usually more light, not a different watering schedule.
- A draft you never feel. A bright spot with an AC vent, radiator or drafty door blowing across it dries leaves and soil on a schedule no care tag anticipates. Airflow and temperature are the usual hidden suspects when light checks out.
The order that solves it fastest
Measure the pot’s own spot first, because it settles both halves at once: it tells you whether the shelf is dimmer than the room feels, and whether the plant standing there is one that a window can overdo. Only then work down the list above.
If you want this answered for your own spot rather than in general, the free spot checker estimates it from your window direction and distance, in your browser.
The lux figures in the tables above are estimates for indoor positions on a clear day and the verdicts come from our own scoring, with temperature, humidity and airflow held at one declared set of values in every row. The six-point readings were measured modestly: a phone laid flat, screen up, at pot height, one room, no laboratory meter. That room’s orientation was never recorded, so those six figures are a measure of how steeply light falls off indoors and not a reading of any particular window.
By GrowSpot · Published July 23, 2026 · Last updated August 30, 2026
