Nothing about the plant changed. It is the same plant, in the same pot, on the same windowsill, being looked after by the same person. What changed is the spot, and it changed in four ways at once while nobody moved anything.
That is the whole difficulty with winter losses. In summer a struggling plant usually has one thing wrong with it and you can find it. In January the light has dropped, the air has dried out, the glass has turned cold and the watering that worked in July has quietly become too much. Each one on its own is survivable. Arriving together, in a plant that is also growing much more slowly, they are not.
Worth a try
It can work here with a little care.
Just the right amount of light
A little cool, but workable
A little dry, but workable
Airflow isn't quite ideal
The light drops, and it drops further than it looks
Shorter days, a lower sun, and more cloud all pull in the same direction. Your eyes will not tell you by how much, because they adjust: a room at a tenth of its summer brightness still reads as “bright enough” when you walk into it.
Here is one ordinary living room, measured on a clear day around midday, phone laid flat at roughly pot height, the same hour for every spot:
| Spot | Reading |
|---|---|
| At the bright window | 20,000 lux |
| 1 m from the window | 15,000 lux |
| 2–3 m away, in window shade | 3,500 lux |
| Middle of the room | 570 lux |
| Darker side of the room | 119 lux |
| The dark corner | 18 lux |
Those are six places in one room on one afternoon, not a summer reading and a winter reading. We have not measured the same room across seasons, and this page is not going to pretend otherwise. What the table is good for is scale. The distance from a window to the middle of a room costs a plant more than a factor of thirty. Winter does something similar to every spot in the room at once, without anyone moving a pot. A plant that was comfortably inside its range in July can be several rungs down that ladder by January while standing exactly where it always stood. The full six-spot walkthrough is here.
This is also why the standard advice, move it closer to the window for winter, is right. It is buying back rungs on that ladder, and the first metre buys the most.
You did not start overwatering. The light changed and the watering did not
Most winter losses get filed under overwatering, and root rot really is where a lot of them end up. But the cause is usually further back than the watering can.
A plant in less light grows more slowly and uses less water. Same pot, same soil, same room, and it is now drinking at maybe half the rate it did in August. If your watering stayed on the schedule that worked all summer, the soil is staying wet longer than it used to, and roots sitting in cold wet soil is the actual mechanism behind most of what people call winter overwatering.
So the fix is not really a watering fix. It is either more light, or less water, and it is easier to be right about which if you know what the spot is currently giving. Water by the weight of the pot and the state of the top few centimetres of soil rather than by the calendar. In winter that usually means longer gaps, sometimes much longer.
The heating dries the air out
Radiators and forced air both drop indoor humidity, often well below what tropical foliage plants are used to. The symptoms are the boring ones people ignore: crisp brown edges, tips that go papery, new leaves that come out smaller and slightly deformed.
Two things make it worse than the raw number suggests. Warm dry air pulls moisture out of leaves faster than cool dry air does, and plants nearest the heat source are usually also the ones on the windowsill, which is where the next problem is.
The sill that was perfect in July is a cold trap in January
Glass is a poor insulator. On a cold night the air in the few centimetres next to a window can sit well below the rest of the room, and a leaf actually touching the pane is colder still. Meanwhile the same sill may get a blast of hot dry air every time the heating cycles on.
Then there are draughts. A gap under a door or a vent aimed at a shelf gives a plant a repeated cold shock rather than a steady cool, and the repetition is the part that does damage. Watch for leaves dropping suddenly without yellowing first, which is a fairly reliable cold signature rather than a watering one.
Nudging a plant a hand’s width back from the glass fixes most of this and costs almost no light, because the steep part of the light fall-off is further into the room than people expect.
What to do, in order
- Re-check the spot rather than assuming it held. The spot is a different place in January than it was in July, and it is the one variable in this list you can actually read instead of guess.
- Move it toward the light if the reading has dropped out of range, and move it properly. A step is not a move. A metre is.
- Stop watering on a schedule. Check the pot instead. Longer gaps, and no standing water in the saucer.
- Get leaves off cold glass and out of the direct path of any vent or radiator. A hand’s width is usually enough.
- Stop feeding until growth picks up again in spring. A plant that is barely growing cannot use it.
- Lower your expectations for new growth. A plant that holds steady through winter and produces nothing is doing fine. Not every dormant plant is a sick one.
Check the spot before you change the watering
No phone to hand? The shadow test gets you the tier with nothing at all.
Which symptom points at which cause
- Stretching, with long bare gaps and small pale new leaves. Light, almost always. The stretch is a readable signal and it is one of the more useful ones.
- Leaning harder than it used to. Also light, and specifically the direction of it. A lean is a direction reading.
- Yellowing lower leaves, soft stems, soil staying wet for days. Water sitting too long, usually because growth slowed and the schedule did not.
- Crisp brown edges and papery tips. Dry air, often plus a radiator underneath.
- Sudden leaf drop with no yellowing first. Cold shock. Look for glass contact or a draught before anything else.
About this article
- What was measured: six spots in one ordinary living room, every place a plant could plausibly stand.
- How: a phone used as a light meter, laid flat and screen up at roughly pot height, on a clear day, the same hour for every spot.
- Sample size: one room, six points. A single sample, not a study: your figures will differ.
- What isn’t here, and it matters on this page: we did not measure the same room in summer and again in winter. The table shows how light falls off across a room, not how far it falls between seasons. We use it for scale and say so, and no number on this page is a seasonal measurement of ours.
- The plant facts: reduced winter light and growth, lower humidity from heating, cold air at glass and the link from slower growth to lower water use are ordinary horticultural consensus rather than our findings.
- Who wrote it: the developer of GrowSpot, working from their own readings rather than reprinted charts.