Your houseplants probably look worse than they did in August. A few lower leaves have yellowed, nothing new has appeared for weeks, and the monstera is leaning at the window as if it wants to leave. Most of that is normal. A British winter cuts the light so hard that most houseplants simply stop growing and wait.
The trouble starts when we try to help. Extra water, a feed, a bigger pot, a move to a “better” spot every few days: a lot of winter losses come from care, not neglect.
This guide covers what’s normal and what isn’t, what central heating actually does to the air in a British home, the cold that catches plants out at night, and the short list of things worth doing. For the month-by-month view of the whole year, see Houseplants Through the British Year.
What’s normal in winter, and what isn’t
Normal, so leave it alone:
- Little or no new growth from November to February.
- One or two of the oldest, lowest leaves turning yellow and dropping. The plant is shedding leaves it can no longer afford to run.
- Stems leaning towards the window.
- Compost staying damp for much longer after watering.
- Flowering plants such as peace lilies stopping flowering.
Not normal, so look closer:
- New leaves, or leaves at the top of the plant, turning yellow or black.
- Stems that are soft or mushy at the soil line, or compost that smells sour. That’s usually root rot from water the plant couldn’t use.
- Dark, greasy or water-soaked patches appearing a day or two after a cold night. That’s chilling damage, covered below.
- Crisp brown edges spreading across many leaves at once, often on the side facing a radiator.
- Fine pale speckling on the leaves, sometimes with fine webbing. Spider mites.
- Small black flies drifting up from the compost when you water. Fungus gnats.
If you’re not sure which list a problem belongs in, the symptom checker works through it from the plant and the symptom. The yellow leaves and brown tips guides go into more detail.
The light problem
Light is the real reason your plants have stopped, and the UK gets less of it in winter than most care advice assumes. At the winter solstice, London has about 7 hours 50 minutes of daylight, Edinburgh about 7 hours and Lerwick under 6. The sun stays low too. At midday in late December it climbs to only about 15° above the horizon in London and about 11° in Edinburgh, against roughly 62° in London in June. Low sun has to pass through far more atmosphere, so it arrives much weaker, and grey winter skies cut it further. The one upside is that a low sun reaches deeper into a south-facing room.
Light also falls away quickly as you move back from the glass: intensity drops with the square of the distance, as the light guide explains. A plant two metres into the room in December may be living on a small fraction of what the windowsill gets.
What helps:
- Move plants to your brightest window for the winter, and closer to it. A south-facing sill that scorched a calathea in July is usually safe from November to February.
- Clean the glass and the leaves. Dust on both cuts light you can’t spare. Wipe large leaves with a damp cloth once a month.
- Turn pots a quarter turn every couple of weeks if a plant is leaning hard.
- Open net curtains and blinds in the day.
- Check what your window actually gives. The light calculator estimates the light at your window for each month of the year. If December falls well short of what a plant needs, a grow light is the only real fix.
Don’t expect growth in December. The aim is to keep plants ticking over until the light comes back in March.
Central heating: what it actually does to your air
“Central heating dries the air” is mostly true, but how dry depends on the house, and that’s worth understanding before you buy anything.
Cold air can’t hold much water. Take a raw British day of 5°C and 85% humidity and warm that air to 20°C: its relative humidity falls to about 32%. On a freezing day of 0°C and 90%, it arrives indoors at about 24%. That’s the dry part.
Then the household adds water back. Cooking, showers, breathing and washing dried on an airer all put moisture into the air. That’s why one British home sits at a dry 30% while the next has condensation running down the windows every morning. Air at 20°C and 50% humidity condenses on any surface colder than about 9°C, which describes a lot of window glass in January.
So the first step is to measure, not guess. A cheap digital hygrometer, around £10, placed next to your plants tells you which kind of house you have. Then:
- 50% or above: fine for almost everything. Humidity isn’t your problem.
- 40% to 50%: fine for most common houseplants, including pothos, monstera, philodendron, snake plants, ZZ plants and spider plants. Calatheas, ferns and prayer plants will start to show brown edges.
- Below 40%: the humidity-lovers will struggle, and spider mites will do well.
What raises humidity, honestly
- A humidifier is the only thing that reliably moves the humidity of a whole room. If you keep calatheas or ferns in a dry house, it’s the fix. The humidifier round-up compares the options, and the calathea humidity guide covers how to run one.
- A bright bathroom is the free option. The RHS notes that many tropical houseplants are best grown in a steamy bathroom, if it has a window.
- Grouping plants together helps a little around the group, because each plant gives off water from its leaves.
- Pebble trays help less than people hope. Our pebble tray calculator works it through: one medium tray in a small 12 m² room adds about 5 percentage points, three trays on a plant shelf about 12, and a single tray in a 35 m² open-plan room under 2. Put your own room in and see.
- Misting wets the leaves for a few minutes and does nothing measurable to the room.
Radiators
The worst spot in a heated home is a windowsill directly above a radiator. The plant gets hot, dry air rising from below, cold glass behind it and a big temperature swing every time the heating cycles. The RHS warns that being too near radiators or fires “can crisp delicate leaves”. Move plants off that sill, or fit a radiator shelf to push the warm air out into the room and away from the leaves.
If your windows stream with condensation
Then dry air isn’t your problem. Cold, wet glass is. Keep leaves from touching the window, wipe the condensation off in the morning, and air the room for a few minutes each day so that mould doesn’t take hold on the sill or in the compost.
Cold: the windowsill at night
Most tropical houseplants come from places that never get cold. University of Florida research on commercial foliage plants puts the damage threshold for most of them at about 10°C. Below that, cells are injured even though nothing freezes. The damage often shows up a day or two later as wilting, water-soaked or greasy-looking patches, and browning. In one trial on Chinese evergreens, dark greasy patches appeared two days after 24 hours at temperatures up to 13°C.
The profiles on this site list a comfortable range for each plant. For the common tropicals the bottom of that range is 15–18°C, for example calathea at 18°C and peace lily at 16°C. The succulents are tougher: jade plant is comfortable down to 12°C and aloe vera to 13°C.
Where the cold catches plants out:
- Behind the curtains. Close the curtains on a winter night and a windowsill plant is shut in with the cold glass, cut off from the warm room. The RHS warns that being left in the cold on windowsills and behind curtains can damage some plants. Either leave that window’s curtains open, or lift the plants into the room in the evening. It matters most with single glazing.
- Leaves touching the glass. A leaf pressed against a frosty window can be damaged even when the room is warm.
- Draughts. Front doors, letterboxes and windows opened to air a room all send cold air across plants.
- Rooms you no longer heat. With heating as expensive as it is, plenty of homes now leave a spare room or hallway cold. Check those rooms with a cheap min/max thermometer before you assume they’re safe. Put the tough succulents in the cool rooms and keep the tropicals in the warm ones.
- Going away for Christmas. Many thermostats ship with frost protection set to 5°C. That protects your pipes, not your plants. If tropical plants stay behind, set the heating to at least 10°C and ideally 12°C or more, or move them all into the warmest room before you go.
- Bringing new plants home. A plant carried from a warm shop through a frosty car park can be chilled in minutes. Ask for it to be wrapped, and get it home quickly.
Watering in winter
Less light means less growth, and less growth means the plant uses less water. The RHS puts it simply: plants growing less “will need less water”. Most houseplants need watering about half as often as in summer, some even less. Succulents and cacti may need almost nothing until March.
Three winter-specific traps:
- The dry surface over a wet root ball. Warm air from a radiator dries the top centimetre or two of compost fast while the middle of the pot stays wet. Push a finger in to the second knuckle, lift the pot to feel its weight, or use a moisture meter to read the root zone.
- Water left in saucers and cachepots. In summer it would evaporate; in winter it sits around the roots. Tip it out after half an hour. The RHS flags plants sitting in water as a winter hazard.
- Ice-cold tap water. Fill the watering can and leave it to stand at room temperature for a few hours. It costs nothing and spares roots that are already cool.
For the full method, see the watering guide. If a plant droops in winter, check the compost before you water. A droop on wet compost means the roots are already struggling, and more water makes it worse. The drooping guide separates the two.
Pests that like a heated house
Two pests do well in a British winter indoors, and both are easier to stop early.
Spider mites. The RHS describes glasshouse red spider mite as thriving “in warm, dry conditions”. It is usually a problem from March to October, but the RHS notes that damage can occur at other times in a heated greenhouse, and a centrally heated living room is much the same set-up. Look for fine pale speckling on the upper side of the leaves and, in heavy attacks, fine webbing. Check the undersides of a few leaves on each plant every week, and raise the humidity around plants that keep getting them.
Fungus gnats. These small black flies breed in damp compost. The RHS notes they are “more numerous in composts that are constantly wet”, which makes them a winter overwatering problem. The adults don’t harm plants; the larvae live in the compost. Let the compost dry out further between waterings. Yellow sticky traps catch the adults, though the RHS warns they catch other insects too, and the nematode Steinernema feltiae watered into the compost deals with the larvae.
The pest field guide covers identification and treatment for both, and the fungus gnats guide has a full four-week plan.
What not to do this winter
The most useful winter care is a list of things to leave alone.
- Don’t feed. A plant that isn’t growing can’t use fertiliser, and the unused salts build up in the compost. Start again at half strength when you see new growth in spring.
- Don’t repot unless you have to. Repotting in winter leaves damaged roots sitting in a big volume of cold, wet compost. The exception is root rot, which can’t wait. Otherwise, the repotting guide is for March and April.
- Don’t expect cuttings to root quickly. Propagation still works in winter, but it is slow and less reliable. Spring is easier.
- Don’t prune for shape. New growth needs light the plant doesn’t have. Remove dead or yellow leaves and leave the rest until spring.
- Don’t keep moving plants around. Every move changes the light the plant has adjusted to. Pick its winter spot and leave it there.
- Don’t water a drooping plant without checking the compost first.
- Don’t buy a fix before you’ve measured. A £10 hygrometer and a £10 min/max thermometer tell you whether you have a humidity problem, a cold problem or neither.
A five-minute weekly check
Once a week from November to February:
- Turn over a few leaves on each plant and look for speckling, webbing or anything that moves.
- Lift each pot. A light pot may need water; a heavy one doesn’t, whatever the surface looks like.
- Tip out any water left standing in saucers or decorative pots.
- Glance at the hygrometer and the min/max thermometer, especially after a cold night.
- Check that no leaves are touching the glass and that nothing sits on a sill above a radiator.
That’s most of winter care. The plants are waiting for March. Your job is to make sure nothing kills them before it arrives.
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