Leaves that turn dark, mushy or see-through after a cold night by the window usually have cold damage, called chilling injury when the temperature stayed above freezing. The damaged patches will not recover, but the plant often can. Move it away from the glass, keep it warm and on the dry side, wait for the damage to finish showing, then trim.
The usual story goes like this: a plant has sat happily on a windowsill since spring, the first properly cold night arrives, and a day or two later some leaves look wet, dark or glassy in patches, or the newest growth has gone limp. The common first reaction is to water it, feed it, or cut everything that looks off right away. None of those help yet. The first job is to confirm that cold is the cause, because the same leaves can look similar after overwatering or root rot.
Quick triage
- Did the damage appear soon after a cold night? Sudden change after a cold spell, a cold car ride or a draft points to cold. Slow decline over weeks points elsewhere.
- Is the damage on the side facing the glass, or on leaves that touched it? Damage that follows the window is the strongest clue.
- Are the youngest leaves worst? In University of Florida trials on dieffenbachia, young leaves were injured first and showed the most severe damage.
- Is the soil soggy and sour-smelling? If so, check the roots. Wet, collapsing growth with rotten roots belongs on the root rot guide, not here.
What cold damage looks like
The University of Florida IFAS Extension describes a chilling temperature as one cold enough to injure a plant but not cold enough to freeze it, usually from just above 32°F to about 59°F. How long the plant sits in that cold matters as much as how cold it gets. On dieffenbachia, the symptoms it lists are yellowing, water-soaked patches and wilted leaves. Water-soaked tissue looks darker and glassy, almost translucent, as if it had been soaked from inside. The American Orchid Society lists similar signs for orchids: surface pitting, sunken areas, discoloration and water-soaking, usually followed by wilting and browning.
Two details make cold damage confusing. First, it is often delayed. The American Orchid Society notes that cold injury usually becomes visible some days after the exposure, not during it. In the Florida trials, some dieffenbachia showed no visible leaf damage at first, while the share of injured leaves went up between 5 and 12 days after chilling. Second, it can reach the stem: the same publication describes a reddish-brown color at the stem base that, in severe cases, spread until the whole stem became water-soaked and collapsed.
1. Leaves touching cold glass
A single pane of glass on a winter night can be much colder than the room air a few inches away. Leaves pressed against it, or tucked between the glass and a curtain, take the worst of it. Iowa State Extension specifically warns against trapping plants between the window and a curtain, because temperatures change a lot from day to night in that spot.
What helps: pull the plant back so no leaves touch the glass, and keep curtains on the room side of the plant at night, not between plant and room.
2. Drafts from leaky frames or opened windows
Cold air sliding in around an old frame, or a window cracked open for airing, can chill a plant even when the rest of the room feels fine. NC State Extension advises keeping houseplants away from cold drafts, heating vents and fireplaces, and notes that sudden temperature changes can cause stress, leading to leaf drop or wilting.
What helps: feel for moving air at plant height on a cold evening. If you can feel it, the plant can too. Move it to a still spot.
3. A cold trip home from the store
A lot of cold damage happens before a plant ever reaches the windowsill. Iowa State Extension recommends boxing or bagging tropical houseplants whenever they will meet even a moment of below-freezing air, and keeping time in a cold car or garage short. The Florida publication also points to unheated trucks, cold loading docks and chilly shops as common sources of chilling injury.
What helps: wrap new plants for the trip in cold weather, and go straight home. If a new plant shows water-soaked leaves a few days later, the trip is a likely suspect.
4. Wet soil going into a cold night
Cold and wet together are harder on roots than either alone. The American Orchid Society advises against watering the day before a cold night. The same idea suits most tropical houseplants on a cold windowsill: winter watering should be lighter anyway, as covered in the guide to overwatering in winter.
5. Sensitive plants in the wrong spot
Some plants handle a cool window better than others. The Florida publication calls dieffenbachia one of the most chilling-sensitive foliage plant genera, and found large differences even between cultivars. NC State Extension notes that jade, spider plants and some kalanchoe often enjoy cooler temperatures, while pothos and monstera prefer warmer conditions. Tropical aroids, calatheas and many orchids are the ones to move back from the glass first.
Cold damage or something else?
| Cause | What you usually see | How to confirm |
|---|---|---|
| Cold damage | Dark, water-soaked or glassy patches, limp young leaves, appearing after a cold spell | Damage is on the window side or on leaves that touched glass; soil is not soggy |
| Overwatering / root rot | Yellowing, soft stems, wilting despite wet soil | Soil stays wet; roots are brown, mushy and smell sour |
| Dry heat from a radiator | Crisp, papery brown tips and edges | Damage faces the heat source and feels dry, not wet |
| Normal winter leaf drop | A few older lower leaves yellow and fall | New growth looks healthy; no wet patches |
What to do after a cold night
- Move the plant somewhere warm and stable, away from glass, doors and vents, but not right next to a heater.
- Do not rush to water. The American Orchid Society advises letting the potting medium dry and holding off on watering until new growth appears. For other houseplants, water only when the top of the soil is dry.
- Skip fertilizer. A stressed plant cannot use it, and the orchid guidance waits for new roots before feeding.
- Wait before cutting. Because symptoms keep developing for days, wait about a week or two so you can see the full extent of the damage.
- Trim what is clearly dead. Remove leaves or sections that have gone fully mushy or brown with clean scissors. Soft, collapsing tissue left in place can rot.
- Check the stem base. A firm stem with damaged leaves usually regrows. A stem that is soft and water-soaked at the base is a much worse sign; take healthy cuttings from the top if the base is failing.
- Watch for disease. The American Orchid Society notes that cold-weakened plants are more prone to disease, so look over the plant every few days.
A simple winter routine to prevent it
- Keep leaves off the glass once nights turn cold.
- Never close a curtain between a plant and the room.
- Check windowsills for drafts on the first cold evenings of the season.
- Wrap plants for any trip outside in freezing weather.
- Water lightly in winter and avoid watering just before a forecast cold night.
- Give the most sensitive plants, like dieffenbachia and other tropical aroids, the warmest bright spot rather than the coldest window.
Related reading: why houseplants drop leaves in winter, crispy leaves near a heater or radiator, the dieffenbachia care guide, the monstera care guide, the pothos care guide, the orchid care guide, the symptom-by-symptom troubleshooting guide and the care guides by plant.
A few things people ask
Will cold-damaged leaves turn green again?
No. Tissue that went water-soaked, black or brown stays that way. The goal is healthy new growth, not saving the damaged leaf.
Can a plant die from one cold night?
It can, especially sensitive plants left in the cold for many hours. In the Florida trials, the most sensitive dieffenbachia cultivar died after chilling at 35°F, while the most tolerant one showed no injury at the same temperature. Most houseplants with a firm stem and healthy roots recover from leaf damage.
Should I move the plant right next to the heater to warm it up?
No. Stable, moderate warmth is the goal. A spot right against a heater swaps cold stress for dry heat, which brings its own problems.
Is it safe to keep plants on the windowsill in winter at all?
Often yes, since light is scarce in winter. Keep leaves off the glass, watch for drafts, and move the most cold-sensitive plants back a little on the coldest nights.
Sources: University of Florida IFAS Extension, Chilling Injury in Tropical Foliage Plants: III. Dieffenbachia; American Orchid Society, Cold Damage; Iowa State Extension, Diagnosing Houseplant Problems from Improper Environmental Conditions; NC State Extension, Winter Care Tips for Healthy Houseplants. Next reads: Why Is My Poinsettia Dropping Leaves?, Why Is My Snake Plant Turning Yellow? and Why Are My Succulent’s Leaves Turning Translucent?.