Houseplant Winter Temperatures | Minimums by Plant, When to Bring Them In, Cold Windows and Floors, Winter Watering and Insulation Tips

Bottom Line: What Temperature Should Houseplants Be Kept At in Winter?

Overwintering houseplants comes down to whether the nighttime minimum temperature drops below each plant's guideline. Many houseplants start to show cold damage at around 10°C.

General guides give a range of numbers depending on the source, such as "5°C or above" or "10°C or above." Neither is wrong.

It helps to read 5°C as the "line that keeps the plant alive" and 10°C as the "line that keeps it healthy." Hyponex says plants lose vigor when the room drops below 10°C.

Here is the key point. Check the temperature where the pot sits just before dawn, not the daytime room temperature.

Even in a room that is warm during the day, the windowsill gets cold at night once the heating is off. Houseplants are usually damaged by cold at night.

This article covers the following, in order.

• When to bring outdoor plants indoors, and how long they can stay outside
• Minimum overwintering temperatures by plant
• Placement that avoids windowsills, floors, and heater drafts
• Winter watering frequency, time of day, and water temperature, and when to stop fertilizing
• Common winter problems, and how to judge cold damage
• Precautions when insulating with plastic or bubble wrap

Every number comes with a source. Our research method is described on About this site.

When Should Houseplants Be Brought Indoors from Outside?

Bring houseplants indoors when nights below about 13°C start to continue. A University of Illinois guide uses 55°F (about 13°C) as the guideline.

The first decision in overwintering houseplants is when to bring them in. October to November, right now, is exactly that time.

The University of Illinois Extension guide puts it this way: once temperatures start to stay below 55°F, it is time to begin moving plants back indoors.

13°C may feel early. Bringing plants in early leaves a margin before the temperature at which houseplants are damaged.

According to the University of Florida, tropical houseplants can be damaged below about 10°C. It also notes that in some species, chilling injury begins at 8 to 12°C.

The surest way to pick the day is by the forecast minimum temperature, not the calendar. Even in the same November, how cold nights get varies greatly by region.

What Should You Do Before Bringing Plants In?

There are two things to finish first: getting plants used to weaker light, and not bringing pests inside. Here are the steps from the University of Illinois guide as a table.

A few leaves may drop after you bring the plant in. Clemson University explains that a major change in environment causes leaf drop.

According to the same source, this leaf drop usually settles down in about 3 weeks. Even if leaves drop right after bringing the plant in, do not rush to change its spot or its watering.

How Long Can Houseplants Stay Outside?

Houseplants can stay outside while nighttime lows stay reliably above about 13°C. Once nights below that start to appear, bring them in, at least at night.

In autumn, even after warm days, cold early mornings become more frequent. Clear nights with little wind get especially cold.

The Japan Meteorological Agency describes radiative cooling as "the ground surface losing heat through radiation, which lowers the air temperature." Colorado State University also notes that frost occurs on clear, calm nights.

Temperatures on a balcony or windowsill are not always the same as the forecast. If in doubt, leave a thermometer that records the minimum temperature next to the pot overnight.

When moving plants outside in spring, follow the steps in reverse. Once nighttime lows stay reliably above the same guideline, acclimate them in the shade.

Sudden direct sun causes leaf scorch. As Iowa State University advises, change the light level gradually.

What Are the Minimum Overwintering Temperatures by Plant?

The overwintering guidelines for each plant are in the table below. Even among houseplants, the guideline temperature and the amount of winter water differ by plant.

Source: Hyponex Plantia care guides, RHS hardiness ratings, ASPCA toxic plant list

The temperatures in the table are guidelines for overwintering indoors. They are not a line where the plant dies the moment the temperature drops below it.

The guidelines are based on these two sources.

• Hyponex care guides for each plant (where they state "X°C and above")
• The cold hardiness ratings of the Royal Horticultural Society (RHS)

In the RHS ratings, H1b is for greenhouses kept at a minimum of 10 to 15°C, and H1c for a minimum of 5 to 10°C. Monstera, pachira, pothos, and Ficus microcarpa are H1b.

The snake plant (sansevieria) is H1c. Manufacturer guides sometimes give lower numbers than the RHS.

You can read the manufacturer's numbers as close to the "line that keeps the plant alive" and the RHS ratings as close to the "line that keeps it healthy." The basic rule is to check that the spot where the plant sits at night does not drop below the temperature in the table.

For plants not in the table, check the tag that came with the plant or the manufacturer's care guide. For a tropical houseplant you are unsure about, a spot that never drops below 10°C is the safe choice.

Also look at the watering column in the table. Even in the same winter, the snake plant needs far less water than the other four.

Source: Hyponex Plantia care guides, RHS hardiness ratings, ASPCA toxic plant list

Hyponex writes this about the snake plant: once it goes dormant in winter, stop watering completely.

Where Should Houseplants Be Placed in Winter?

The basic rule for winter placement is a bright spot by the window during the day and the middle of the room, away from the window, at night. Do not set pots directly on the floor, and pick a spot out of the heater's airflow.

There are three cold spots in a home in winter: by the window, on the floor, and in the entryway. The spot that gets too dry is in front of the heater's airflow.

Winter days are short and the light is weak. A window is the best place to catch daytime light. The figure below shows roughly how brightness changes with distance from the window.

How Cold Does a Windowsill Get at Night?

At night, the area by the window gets colder than the middle of the room. Hyponex also warns that windowsills and entryways can get cold without you noticing.

According to Panasonic, more than half of the heat from winter heating escapes through openings such as windows. In a study of a home with single-pane glass, the figure was 58%.

Where heat escapes is also where outdoor cold gets in. At night, the area by the window is colder than the room thermometer shows.

The fix is to move the plant from the window to the middle of the room in the evening. For heavy pots you cannot move, close thick curtains and keep the plant on the room side.

The key is not to leave plants between the curtain and the window at night. The space behind the curtain becomes a channel for cold air.

Why Is Heater Airflow Bad for Houseplants?

Because it draws water from the leaves faster than the roots can take it up. Leaf tips turn brown, and the soil dries out quickly.

The University of Wisconsin explains that dry indoor air draws water from leaves. It notes that brown leaf tips are common during the winter heating season.

Indoor humidity drops a lot in winter. Here are the figures.

• University of Illinois: indoor humidity in winter can fall to 10 to 20%
• Purdue University: dropping to 15% during the heating season is not unusual
• Purdue University: most houseplants grow well at 35 to 45%

Hyponex's Ficus microcarpa guide also says to avoid spots where heater air blows directly on the plant. If damage starts at the leaf tips, also see Why leaf tips turn brown.

On the other hand, there is no need to keep things very warm through the night. The University of Illinois says houseplants prefer nights about 5°C cooler than the day.

The University of Wisconsin also says that nights that are too warm make the plant use up its reserves quickly and weaken. It is fine to turn the heating off at night. What you need to protect is the minimum temperature in the table.

Why Is the Floor Cold?

Because cold air is heavy and spreads along the floor. Air cooled by the window flowing downward is called a cold draft.

Panasonic explains the mechanism this way. Cold air moves down and warm air moves up. Air cooled at the window spreads into the room along the floor.

Even with the heating turned up, the area near the floor tends to stay cold. A pot set directly on the floor sits in that cold air.

The easiest fix is to put the pot on a stand to lift it off the floor. A sheet of styrofoam or a board under the pot also keeps the floor's cold from passing into it.

How Often, When, and at What Water Temperature Should You Water Houseplants in Winter?

In winter, wait a few days after the soil is dry deep down, then water during a warm part of the day with room-temperature water. Do not water by the calendar; check the soil with your finger.

How Often Should You Water in Winter?

In winter, water about 2 to 3 days after the soil surface dries. Hyponex says winter watering, in both amount and frequency, should be half of summer or less.

Growth slows in winter, and the roots take up less water. Water stays in the soil longer, which makes root rot more likely.

Heated rooms are an exception, though. Purdue University notes that dry air can mean watering more often than in the growing season.

Here is the key point. Do not decide winter watering by "how many times a week"; check the soil with your finger every time. The University of Illinois also recommends pushing a finger into the soil up to the second knuckle.

What Time of Day Is Best for Watering in Winter?

Water during the day, while the heating keeps the room warm. That gives excess water time to drain from the pot before the cold of night.

Few primary sources state the time of day clearly. This advice is reasoned from the following sources.

• Clemson University: too much water reduces oxygen around the roots and makes root diseases more likely
• Clemson University: wet soil, low light, and low temperatures together make bumps (blisters) on leaves more likely
• University of Florida: after cold damage, watering in the morning is recommended

Watering in the evening means the soil is still wet when the coldest hours arrive. In winter, it is safest to avoid watering from evening on.

What Water Temperature Is Best?

Use water that has come to room temperature. Cold water on the leaves can leave whitish spots.

Clemson University explains that cold water causes white to straw-colored spots on leaves. Hyponex also says to use room-temperature water for misting leaves.

Tap water gets cold in winter. An easy method is to fill the watering can the night before and leave it indoors.

Should You Keep Misting Leaves in Winter?

Misting helps prevent dry leaves and spider mites, so it is fine to keep doing it in winter. It does very little to raise room humidity, though.

Hyponex's Ficus microcarpa guide says misting also helps prevent spider mites. On the other hand, the University of Illinois notes that the humidity from a spray bottle lasts only a few minutes.

To raise humidity, you can use these methods from the University of Illinois.

• Group several pots together
• Set the pot on a tray of pebbles filled with water (keep the water below the top of the pebbles)
• Keep the plant in a humid room, such as near the kitchen or bathroom

Mist during the warm part of the day so the leaves dry by night. This keeps leaves from going into the cold night wet. If watering has damaged the roots, see How to spot root rot.

When Should You Stop Fertilizing Houseplants?

Stop fertilizing houseplants around the time you bring them indoors, and restart in spring once new buds start growing. In winter, growth is slow and plants cannot use up the fertilizer.

The University of Illinois says to stop fertilizing until spring once plants are brought indoors. The University of Wisconsin also says to resume only once plants start growing actively in spring.

Hyponex also says fertilizer is for spring to autumn and is not needed in winter. The reason is that unused fertilizer stays in the soil.

According to the University of Nebraska, fertilizing a dormant plant causes salts to build up in the soil. High salt levels damage the roots directly.

Do not add fertilizer just because a plant looks weak in winter. Adding it to a weak plant lets the salts damage the roots and makes things worse.

What Problems Are Common in Winter?

The three common winter problems are leaf drop, root rot, and spider mites. Their causes are, in turn, cold or being moved, water left in the soil, and dry air.

Why Do Leaves Drop in Winter?

Leaves drop in winter mainly because of cold and changes in environment. If it happens after bringing the plant in or moving it, watch it for about 3 weeks.

Clemson University says leaves drop when a plant gets chilled. Hyponex's Ficus microcarpa guide also says it drops leaves in the cold.

The same guide says it also drops leaves right after purchase or after being moved to a new spot. Bringing plants in for winter is a time when both happen at once.

If the trunk and base are firm, there is a good chance new buds will grow in spring. For telling causes apart by where the yellowing appears, see Why leaves turn yellow.

Why Does Root Rot Increase in Winter?

Because people keep watering as in summer even though the roots take up little water in winter. Water stays in the cold soil, and the roots cannot breathe.

Hyponex's winter care guide says plants that die in winter are often killed by a watering problem. It recommends cutting back the amount or frequency of watering.

Clemson University also says overwatering reduces oxygen to the roots and invites root disease. If the base of a plant feels mushy in winter, stop watering first.

Why Do Spider Mites Appear in Winter?

Because air dried by heating makes it easy for spider mites to multiply. Checking leaf undersides every time you water helps you notice them early.

Purdue University says spider mites favor hot, dry, stagnant air. A heated room in winter fits that description.

Clemson University describes spider mite symptoms as follows.

• Pale specks appear on the upper side of leaves, and the whole leaf looks faded
• In heavy cases, fine thread-like webbing is visible
• If left alone, the leaves turn yellow

The first step is to move any suspect plant away from the others. Then rinse both sides of the leaves with water.

How Do You Judge a Houseplant Damaged by Cold?

Do not judge right after cold damage; wait about 3 to 7 days in a warm spot before checking. If the tissue under the bark of a stem or trunk is green, that part is alive.

The University of Florida lists these symptoms of chilling injury.

• Leaves suddenly wilt
• Water-soaked areas appear on leaves
• After it warms up, the damaged parts turn brown

According to the same source, plants can recover if the chilling was brief. Damage that slows growth may still remain, though. Long exposure to cold causes damage that cannot be reversed.

Another University of Florida article (on landscape plants) explains how to check plants after a cold spell. The same approach works for potted houseplants.

• Damage looks worse right afterward. Wait at least 3 to 7 days before judging
• Lightly scrape the bark. Green underneath means alive; brown or black means damaged
• If in doubt, do not cut branches until new buds appear
• Wait to fertilize until growth resumes in spring

Here are the steps.

1. Move the plant to the middle of the room, out of heater airflow
2. Water sparingly, only after the soil dries
3. Remove damaged leaves only once they have turned completely brown
4. Cut branches or stems only after new buds appear and you can see which parts are alive
5. Fertilize and repot once buds start growing in spring

It is not too late to decide a plant is "dead" after seeing whether buds grow in spring. Even if damage reaches the base, some plants can be restarted from cuttings as long as green stems remain.

For when and how to repot, see How to repot.

What Should You Watch for When Insulating with Plastic or Bubble Wrap?

Put up supports so the cover does not touch the leaves, and open it on sunny days to let heat out. A cover raises the temperature only slightly, so bring plants indoors on very cold nights.

In a Colorado State University test, a plastic cover on a frame gave about 2 to 3°C of protection. The original figure is a little over 3 to 6°F.

The same source says plants freeze where the cover touches them, so the cover should be kept off the plant. It also says to open it during the day, leaving at least a gap, so heat does not build up.

The University of Florida also says not to let the cover touch the plant directly. Anchor the cover to the ground and remove it in the morning once temperatures start to rise.

Can Houseplants Overwinter in an Outdoor Plastic Greenhouse?

Overwintering tropical houseplants in an unheated plastic greenhouse alone is often difficult. It adds only about 2 to 3°C, so add that to the forecast low and see whether it reaches the plant's guideline.

For example, if the forecast low is 3°C, it will be only about 5 to 6°C inside the cover. Bring plants indoors if that falls short of their guideline in the table above.

Thinking of a plastic greenhouse as a stopgap until plants come indoors helps avoid failure. On sunny days, open it so it does not get too hot inside.

How Should You Use Bubble Wrap?

There are two uses: wrapping the pot so the roots do not get cold, and sticking it on windows to soften cold air. Do not leave the leaves wrapped in it.

The bubbles in bubble wrap form a layer of air that slows heat transfer. Wrapping the pot keeps the soil temperature from dropping.

Sticking it on window glass softens the flow of window-chilled air down to the floor. It is the cold draft remedy described by Panasonic.

When wrapping a pot in bubble wrap, the key is not to block the drainage hole. If water cannot drain, it can lead to root rot in winter.

Can You Cover a Plant with a Plastic Bag?

Yes, if you cover it only at night, with supports so the bag does not touch the leaves. Remove it in the morning and never leave it on in sunlight.

Where a plastic bag sticks to leaves, cold passes through at that spot. It is the same thing Colorado State University describes: plants freeze where the cover touches.

In sunlight, the inside of the bag heats up fast. Always pair the two steps: cover at night and remove in the morning. If you worry about forgetting to remove it, simply moving the plant away from the window is the better option.

What Should You Review While Overwintering Houseplants?

Going through the table below from top to bottom once a month helps avoid winter failures. When a cold snap is forecast, at least check where the plants sit at night.

What matters in overwintering is not adding things but "not letting plants get cold or too wet." Once buds start growing in spring, bring the plants back to full health with fertilizer and repotting.

What Terms Come Up When Overwintering Houseplants?

Frequently Asked Questions About Overwintering Houseplants

How Cold Can Houseplants Tolerate?

It depends on the plant. The guidelines for each plant are in the table above.

For a tropical houseplant with no known guideline, keeping its nighttime spot at 10°C or above is the safe choice. The University of Florida says damage may occur below about 10°C.

Can Houseplants Overwinter Outdoors?

Overwintering tropical houseplants outdoors is difficult. Once nighttime lows start dropping below about 13°C, bring them indoors.

An unheated plastic greenhouse adds only about 2 to 3°C. If the forecast low plus 2 to 3°C still falls short of the guideline, bring the plants indoors.

Is It Enough to Keep Houseplants by the Window in Winter?

During the day, a bright spot by the window is good. At night, though, move them away from the window toward the middle of the room.

A windowsill is good for catching daytime light but gets cold at night. Changing spots between day and night is the basic rule in winter. For pots you cannot move, close the curtains at night and keep the plant on the room side.

Is It OK to Turn Off the Heating Only at Night?

Yes, as long as the temperature where the plant sits does not drop below its overwintering guideline.

The University of Illinois says houseplants prefer nights about 5°C cooler than the day. What you need to protect is the nighttime minimum; there is no need to heat all night. On cold-snap nights, move plants away from the window and set them on a stand.

Can You Repot in Winter?

If possible, wait until spring. In winter, roots are sluggish and plants take longer to recover from the stress of repotting.

Even for a root-bound plant that no longer soaks up water, it is safer in winter to water sparingly and wait for spring. Repot once new buds start growing. For the steps, see How to repot and Choosing soil for houseplants.

Can Houseplants Overwinter in an Unheated Room?

Yes, if the nighttime low does not drop below the plant's guideline. First, measure it overnight with a thermometer.

An unheated room also has the advantage of less worry about dryness and spider mites. If some nights drop below the guideline, move the plant to a warmer room just for those nights. Simply moving it away from the window and lifting it off the floor makes it less cold.

What Else Should You Read?

Sources

• University of Illinois Extension: Tips for moving houseplants indoors and overwinter care (bringing plants in at 55°F, acclimation, pests, isolation, winter water and fertilizer, humidity)
• UF/IFAS Extension: Cold Protection of Foliage Plants in Shadehouses and Greenhouses (damage below about 10°C, chilling injury temperatures and symptoms)
• UF/IFAS Extension Miami-Dade: Good Strategies for Cold Damage in the Landscape (wait 3 to 7 days, green under the bark, when to prune and fertilize)
• UF/IFAS Extension Leon County: Frost in the Panhandle? Practical Tips for Protecting Your Garden (keep covers off the plant, anchor them to the ground, remove in the morning)
• Colorado State University Extension: Frost Protection and Extending the Growing Season (effect of plastic covers, keep them off the plant, open during the day, radiation frost)
• Clemson University HGIC: Houseplant Diseases & Disorders (leaf drop from chilling, leaf drop from environmental change, cold water spots, overwatering)
• Clemson University HGIC: Common Houseplant Insects & Related Pests (spider mite symptoms and isolation)
• Purdue University Consumer Horticulture: Thirst Aid for Houseplants (indoor humidity in winter, spider mites)
• University of Wisconsin-Madison Extension: Keys to Healthy Houseplants (dry air, overly warm nights, winter fertilizer)
• University of Nebraska-Lincoln Extension: Success With Houseplants - Fertilization (fertilizing during dormancy and salt buildup)
• Iowa State University Extension: What causes leaves on my houseplant to turn yellow or brown and drop off? (change the light level gradually)
• Japan Meteorological Agency: Forecast terms, air temperature (in Japanese. Radiative cooling)
• Panasonic: Why a room stays cold even with the heating on, and budget-friendly ways to keep warm (in Japanese. Cold draft, heat loss through openings)
• Hyponex Plantia: Tips for caring for houseplants in winter without killing them (in Japanese. 10°C, winter watering, saucers)
• Hyponex Plantia: 18 cold-tolerant houseplants and key points for overwintering (in Japanese. Cold windowsills and entryways, winter watering, no extra fertilizer)
• Hyponex Plantia: How to care for houseplants (in Japanese. Winter watering frequency, room-temperature water, when to fertilize)
• Hyponex Plantia: How to grow Ficus microcarpa (in Japanese. Cold by the window, heater airflow, misting and spider mites, leaf drop)
• Hyponex Plantia: How to grow pachira | Is watering the reason it dies? (in Japanese)
• Hyponex Plantia: How to grow and repot sansevieria (in Japanese. No watering while dormant)
• Hyponex: How to grow Monstera and growing tips (in Japanese. Fertilize from spring to autumn, not needed in winter)
• Hyponex: Hyponex Original Liquid (in Japanese. Use after repotting)
• RHS: Monstera deliciosa
• RHS: Pachira aquatica
• RHS: Epipremnum aureum
• RHS: Ficus microcarpa
• RHS: Dracaena trifasciata