Search this and you get lists. Five reasons, seven reasons, ten reasons: impoverished soil, the wrong pH, nutrients present but unavailable, root-bound pots, transplant shock, the wrong season, too much water, too little. Every list is accurate. None tells you which line is yours.
Most of them are also answering about a garden. The threads on the first page are about vegetable beds and crops that have not gained four inches in two months, and Google splits out an indoor version of the question as a search of its own. Indoors the list is shorter, and one item on it can be settled with a number rather than a guess.
Great fit
This plant should be happy in this spot.
Just the right amount of light
Comfortable temperature
Humidity suits it
Airflow isn't quite ideal
Most of the time the room is not the reason
Here is an ordinary indoor spot, three metres into a room with a south window, with seven different plants standing in it one at a time. Nothing about the room changes down the table.
| The plant standing there | What the light is doing | Verdict |
|---|---|---|
| Monstera | Just the right amount of light | Great fit, 94/100 |
| Golden pothos | Just the right amount of light | Great fit, 94/100 |
| Snake plant | Just the right amount of light | Great fit, 94/100 |
| ZZ plant | Just the right amount of light | Great fit, 94/100 |
| Peace lily | Just the right amount of light | Great fit, 95/100 |
| Fiddle leaf fig | A little dim, but workable | Worth a try, 67/100 |
| Jade plant | Too dim here | Not the best fit right now, 44/100 |
Five of the seven are fine there. The fiddle leaf fig is not, and the jade is not remotely. So the honest answer to “is my spot the problem” depends entirely on what is standing in it, which is the one thing a list of ten causes cannot tell you and a score can. If your plant is one of the five, you have crossed one item off a list of ten, which is worth more than it sounds when checking the other nine means disturbing the plant. If it is growing but stretching rather than filling out, that is a different symptom with a much narrower list.
The figures are estimates rather than meter readings. We build them from the window direction, the distance and a clear day, on the same curated care data the app scores with; your own spot will read differently, which is what the free checker is for.
Both ends of the room are flagged, and the reflex goes the wrong way
The instinct, when something is not growing, is to move it nearer the window. Here is what that walk actually costs, with the same plant and the same room:
| How far into the room it is | Estimated light | What the light is doing | Verdict |
|---|---|---|---|
| 0.3 m, against the glass | 13,000 lux | A bit bright, but workable | Worth a try, 66/100 |
| 1 m back | 10,000 lux | Just the right amount of light | Great fit, 94/100 |
| 2 m back | 6,300 lux | Just the right amount of light | Great fit, 94/100 |
| 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 |
| 5 m back | 1,575 lux | A little dim, but workable | Worth a try, 66/100 |
Read the ends. Against the glass it is flagged at 66, and five metres back it is flagged at 66, and everywhere between one and four metres it holds 94. The room has a wide comfortable middle and two bad edges, and the reflex move, from the middle towards the window, is a move from 94 to 66. A little dim and a bit bright are both flags; only one of them looks like a problem from across the room.
That matters because relocation is itself on every one of those cause lists. Move a stalled plant on a hunch and you can end up holding two problems: the original one, undiagnosed, and a fresh one you introduced. Reading the spot first is the cheap half of this.
When the light checks out, the flag can be somewhere else you can measure
Crossing light off is not the same as crossing the spot off. Here is a prayer plant one metre from an east window, in light it is entirely happy with, with only the air in the room changing:
| How dry the air is there | What the light is doing | Verdict |
|---|---|---|
| 20% | Just the right amount of light | Worth a try, 66/100 |
| 25% | Just the right amount of light | Worth a try, 66/100 |
| 30% | Just the right amount of light | Worth a try, 66/100 |
| 40% | Just the right amount of light | Worth a try, 66/100 |
| 50% | Just the right amount of light | Great fit, 91/100 |
| 60% | Just the right amount of light | Great fit, 100/100 |
The light column reads the same on every row, all the way down. The verdict does not: it sits at 66 through 40% humidity and only clears once the air comes up. A spot can pass on light and still be the reason nothing is happening, and dry air is the version of that people are least likely to suspect in a room that feels comfortable to them.
What this cannot tell you
It cannot see the pot, so a root-bound plant reads the same as a comfortable one. It cannot see the soil, so nutrients and pH sit outside it entirely. It cannot see pests. And it does not know what month your plant thinks it is: one that stops in November and starts again in March is doing the correct thing. The seasonal version is a separate page, because the fix is different. If the spot scores well and nothing has moved in three months, that is real information: stop rearranging the room and look at the roots.
Published August 19, 2026
