Plants that live indoors with us over the winter — both houseplants and those that are only stored inside the house seasonally — need a few things from us to get through the darker, colder months. At the same time, too much coddling during this period of semi-dormancy can doom plants. This week, I am sharing how to prepare plants for the transition and how to strike the right balance to keep them happy and healthy.
I will be upfront and tell you that this week’s episode merits a 🚨geek alert🚨 because I will also discuss the science behind successful cool-season care of indoor plants. When you understand the underlying science, implementing these tips will feel intuitive. I also encourage you to use your instincts and observational skills to help you realize that you don’t need to be so hands on with these plants once they’re inside.
Houseplants need less attention in winter when they are dormant, but there are a few things you should do to prepare them for the change in seasons.
Both houseplants that are already inside and the tender plants that we bring in just for the winter need to be prepared for the change in seasons and the limitations and complications of being indoors. We need to do some preparation to improve their environment so they can survive.
Before continuing, I want to take a moment to let you know that on Wednesday, November 19, at noon Eastern, I will be co-hosting a webinar on co-existing with deer and other mammals. Nancy Lawson, the Humane Gardener, will join me for this session. The cost is $29 plus processing fees. Learn more about and sign up for “Who’s Nibbling in Your Garden?” at this link.
Moving In Is a Big Shock
Moving a plant inside that’s spent most of the year outdoors — that’s quite a shift. Kind of a shock, actually. And there are some things that we need to do before we ever bring them in. It’s not like you snap your fingers and suddenly they’re inside from outside. They need more acclimation time.
It’s like hardening off seedlings in reverse. Seedlings raised under artificial light outdoors will get light burn if they are moved outdoors into direct sunlight and left there all day. They need to be introduced to the sun gradually — no more than 30 minutes in direct sunlight on that first day. Any more will be a huge shock to their systems, and it can take weeks for them to bounce back.
Likewise, moving a plant from an outdoor environment to an indoor environment is shocking. There is a drastic drop in lighting and the humidity can also be much lower than what a plant was accustomed to.
Ease plants into living indoors. This helps them adjust to their future environment slowly but surely, as the plants can sense the change. They have physiological systems that can detect shorter days and cooler temperatures. Phytochrome, a photoreceptor protein found in plants, is light sensitive. It tells the plant cells that things are changing, the day length is shortening and the light quality is reducing.
In response to receiving less light, a plant’s metabolic activity changes. It slows down. Leaf expansion, flowering and fruiting stop. Its needs are far less than what they were when the plant was in full growth mode and busy with photosynthetic activity. So we need to adapt to their slowing down. They don’t need proactive attention from us. We have to back off from watering and cease fertilizing during this period. In winter, plants are not all that interested in a lot of TLC other than proper stable conditions. It’s human nature to want to nurse them along, but they don’t need it.
After living outdoors for the spring and summer, moving inside in fall is a big adjustment for a plant.
Photo Credit: Amy Prentice
Indoors, Light is Far, Far Less Intense
The light quality inside a house is dramatically different than it is outdoors. Under a basic grow light, the light quality is at least 90% less than the sun provides. Although a basic grow light is sufficient to help a plant grow in the early stages, a more mature plant needs more to kick in the growth mode.
If you’re bringing plants indoors for the winter, one of the best things you can do is group them right in front of a bright, south-facing window. That’s usually the best spot in the house for light. Even with modern UV-blocking windows, the quality of light that plants need to get through the cool season isn’t filtered out in any meaningful way. For many houseplants and overwintered container plants, that natural sunlight is often enough to keep them healthy until spring.
But not every window delivers the same amount of light, and not every plant has the same light needs. If your plants are stretching toward the window, putting on weak new growth, or simply stalling out, that’s a sign they may not be getting enough light.
Group houseplants and overwintering tender plants by a south-facing window so they get the most light they can get from the sun.
Photo Credit: Huy Phan ( Pexels)
Here’s a simple rule of thumb: On a sunny day, if you can comfortably read a book by that window without turning on a lamp, you’re probably getting around 100–300 micromoles of light. That’s good for most foliage plants. But plants that love full sun — like citrus and peppers — may want more.
That’s where a supplemental grow light comes in. Adding a full-spectrum LED over the group for 12 to 16 hours a day can make up the difference, especially during the short, low-light days of winter. It doesn’t have to be complicated or fancy — just enough to boost the overall light intensity so those plants stay happy and strong until it’s time to head back outside in spring.
LED grow lights supplement sunlight that comes in from windows.
Photo Credit: PP (via Canva)
Check Plants Before Bringing Them Indoors
Before bringing a plant indoors, consider what may have been living on those plants along the way. There are a lot of very tiny insects that could hitchhike indoors.
Inspect plants for hitchhikers before moving them inside.
Photo Credit: Amy Prentice
You can cleanse your plant of insects with a good blast of water. A stiff blast works wonders to remove uninvited guests.
Look underneath leaves and in tight quarters like leaf nodes where insects may be hiding.
Spraying down a plant with a sharp stream of water can knock off pests before bringing a plant indoors. Photo Credit: Amy Prentice
If you felt like you needed more than just a stiff blast of water, you could literally submerge the plant in a big bucket of warmish water and allow anything that’s hanging on tight to dislodge and float away.
Another concern is overwintering insects that have already made their way into the soil. When they are moved into a heated house, they may think it is spring and break dormancy.
You could lift out the plant from the container and inspect the roots and the soil — and this wouldn’t be a bad time to go ahead and refresh the soil or cut out dead roots.
Take plants out of their container to inspect the roots for damage or pests before bringing a plant indoors.
Photo Credit: Karola G (Pexels)
You might want to clean the containers too because there could be pathogens that are hitchhiking in too. One that may be most prevalent is fungal diseases. Soap and water, or water with a little vinegar or a little hydrogen peroxide will cleanse the pots of pathogens.
Giving plants a good cleaning before moving them indoors can reduce the risk that plants become infected by fungus and other pathogens.
Photo Credit: Amy Prentice
Respiration and Transpiration Slow Down in Winter
Plants are living things, and they breathe. In winter, the plants are breathing slowly to conserve energy and moisture to survive a lean season.
If available light is so low that the photosynthesis rate is less than the respiration rate, there is a deficiency. The compensation point is where respiration is greater than the photosynthesis. If it’s not in balance — if the light is lower than the respiration level — then there’s an energy deficiency in the plant, and that’s when you can see signs of stress.
Maybe the leaves are yellowing or they become less turgid (stiff). Those are biofeedback signals for you to pay attention to.
If there is a deficiency, here’s what you don’t want to do. You don’t want to over water and you don’t want to fertilize the plant. More plants die from overwatering than under watering. Especially during the time of year where the plants are going into dormancy, they do not need much water at all. Just a little bit, periodically.
The first thing I want you to do is stick your finger into the soil. The finger test is always the best test to see what the condition of the soil is as far as moisture. But in the wintertime, even if it comes back dry, that’s okay. Plants are only taking up very minimal amounts of water during this time.
Stomatal conductance drops in winter. That means transpiration — the release of moisture from the leaves of the plant through the stomates — slows down.
Stomates look like little mouthparts. They’re on the underside of the leaf. You usually can’t see them with a naked eye, but they’re there. Those stomates have guard cells around the edges that control whether they’re open or closed. During this time of the year, they’re mostly closed. So the moisture that normally would leave the leaves throughout the normal growth cycle, it’s very reduced, and the roots are absorbing less water. But overwatering would suffocate the roots because watering displaces air that’s in the soil.
Hoya plants. Like other houseplants, during the winter when they get less light, they aren’t photosynthesizing as much and don’t need much water at all.
Photo Credit: Jobrestful (Getty Images)
Humidity, Temperature and Air Circulation
For houseplants, the ideal temperature is somewhere around 65 to 75°F, give or take. The plants are pretty forgiving there. And at night, it would be nice if it was a little bit cooler, maybe 55 to 65°.
You want to avoid two extremes: cold drafty conditions, or hot furnace blasts. So don’t keep plants by an exterior door or a heating vent or radiator. Air circulation will help to prevent fungus from establishing on plants, but cold drafts or blasting heat will stress plants.
Find that sweet spot, that Goldilocks spot, not too cold, not too hot, but right in the middle. And that will suffice for temperature.
Humidity is the important thing. In the wintertime, that’s the one that gets most houseplants. The way our houses are heated, it dries the moisture out. A comfortable level for humidity is probably around 55 or 60%. In the wintertime, indoor humidity usually drops to closer to around 30%.
If plants are unhappy with low humidity, they will show it. They may look wilty or just not good in general.
There are no magic elixirs to fix the problem such as misting your plants every day or putting a solid tray underneath your pots with some stones and water. That can help a little bit, but not as much as we would like to think it does.
You could get a humidifier, but even that added moisture dissipates quickly and disperses rapidly. So set a humidifier right next to your plants for the best hope of making a difference.
How to Prepare Indoor Plants for Vacation
If you are going away for a week or more in winter, you can gather up your plants and put them in your bathtub, plug the drain, put a little water in the tub and close the door or curtain. This will keep that environment humid during that time that you’re gone.
Those containers should not sit in the water. The containers should be propped up so the soil is not drawing water.
Don’t Apply Fertilizing During Dormancy
When plants have slowed down and are not actively growing, they don’t need fertilizer. In fact, adding fertilizer can really do more harm than good. It can cause excess salt buildup in the soil and can potentially stimulate growth at the wrong time.
Roots can’t process fertilizer efficiently when they’re dormant or semi-dormant. Pause the feeding until they’re getting ready to go back outside. And then you can slowly ease them back into receiving fertilizer. But not until then.
A monstera plant. In the winter when it is not actively growing, refrain from applying fertilizer.
Photo Credit: Russell Prentice
It’s Not the Time for Pruning
When getting ready to move a plant inside, refrain from pruning.
The worst time of the year to prune is in the fall as plants are going dormant. Growth follows the cut. When you make a pruning cut on a plant, there’s a hormone that’s removed, and that removal enables new growth to happen.
This is a bad time for new growth outdoors because those new branches will be unable to be conditioned enough to survive cold weather. Because it’s still tender, it can die off and that can expose an entry point for pests or diseases. And for plants that are headed indoors, new growth just as the plants are becoming dormant will throw off their natural systems.
Of course, you can remove anything that is dead, diseased, rotting or going yellow. Yellow leaves are done photosynthesizing, so there’s no benefit to keeping those leaves on the plant.
Cleaning Houseplants
Plants collect dust, and that dust layer will block some light and get in the way of photosynthetic activity. One of the best hands-on things you can do is clean the leaf surface with a damp paper towel or a soft cloth to remove accumulated dust.
Control Fungus Gnats and Other Houseplant Pests
Among houseplant pests, spider mites are a big one and you may also encounter whitefly, mealy bugs, aphids, pill bugs, slugs, earwigs and thrips. But the biggest nuisance inside is fungus gnats. Fungus gnats love moist soil. That’s where they lay their eggs. Are you watering too much? Backing off on watering could resolve the issue.
Whiteflies, which are related to aphids, are commons houseplant pests.
Photo Credit: Thomas Klejdysz from Getty Images
If you continue to see fungus gnats, there are other control methods you can use. One of those is Mosquito Dunks, the brand name for Bti, or Bacillus thuringiensis israelensis, a bacteria used for biological control of mosquitoes and gnats.
Mosquito Dunks contain Bti, a biological control for fungus gnats.
You can grind the dunks up or crush them and mix them with water and pour them in. Yes, you don’t want to overwater, but this is how you get the Bti down into the soil to control fungus gnat larvae.
Yellow sticky traps offer a solution that doesn’t require any watering. I don’t like sticky traps outdoors because they are a nonselective means of pest control. But indoors, you won’t have the problem of unintentionally catching beneficial insects. The traps are super sticky, and insects are very much attracted to the color yellow. You can discreetly place them near the plants without them being an eyesore.
Yellow sticky traps are a water-free control method for fungus gnats and other flying insects.
Photo Credit: Amy Prentice
You can also buy beneficial nematodes — little microscopic worms — in a packet of powder that you mix with water then pour into the soil.
Insecticidal soap is a refined soap with a little bit of oil or surfactant that causes the active ingredient to stick. This is used not on the soil but on the above ground portion of the plant. Neem oil, a natural derivative of the neem tree, is used in a similar way to insecticidal soap. When using either spray, don’t do it in the living room or wherever the plants stay. Bring the plants to a garage, porch or outside on a warm day to spray them, applying to the tops and bottoms of leaves.
Spider mites are common houseplant pests.
Photo Credit: Amy Prentice
Houseplant Picks
Here are five types of low-maintenance houseplants to get you started:
Sansevieria, or snake plant, aka mother-in-law’s tongue. I have one that i call “Sansi.” He lives in my office opposite my desk, with a light that’s on just during the day. This plant goes months between watering. Sansevierias are crazy drought tolerant. It’s an old-time classic you can’t go wrong with, and it’s got a really neat structure.
Pothos are viney houseplants that perform well with very little care.
Spathiphyllum, or peace lily, is a flowering houseplant.
Philodendrons come in very pretty big-leaf varieties.
Hoyas are viney and flowering.
The peace lily is a classic and reliable houseplant.
Photo Credit: Thang Nguyen (Pexels)
I hope you enjoyed my tips on maintaining houseplants and overwintering tender plants. If you haven’t listened yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
How do you take care of your indoor plants in winter? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
Episode 81: Growing Indoors: The Basics of Houseplant Care and Maintenance
Episode 83: Gardening Indoors: The Science of Light, with Leslie Halleck
Episode 108: Easy Ways to Make More Houseplants, Vegetables and Flowers
Episode 139: Houseplant Myths: The Facts Behind Caring for Indoor Plants
Episode 178: Selecting and Caring for Houseplants, with Jane Perrone
Episode 255: Raising Carnivorous Plants, with Kenny Coogan
Episode 263: Growing Joy: How Plant Care Can Be Self Care, with Maria Failla
Episode 337: Legends of the Leaf: The Secrets of Well-Known Houseplants, with Jane Perrone
joegardenerTV YouTube: What to Look for When Buying Plants
“Who’s Nibbling in Your Garden?” webinar on Wednesday, November 19, from noon to 1:30 p.m. Eastern with Nancy Lawson.
joegardener Online Gardening Academy™: Popular courses on gardening fundamentals; managing pests, diseases & weeds; seed starting and more.
joegardener Online Gardening Academy Organic Vegetable Gardening: My new premium online course. The course is designed to be a comprehensive guide to starting, growing, nurturing and harvesting your favorite vegetables, no matter what you love to eat, no matter where you live, no matter your level of gardening experience.
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Learn how to grow epic tomatoes with Joe Lamp’l and Craig LeHoullier.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
Mosquito Bits for fungus gnat control
Mosquito Dunks for fungus gnat control
Disclosure: As an Amazon Associate, I earn from qualifying purchases. I receive a commission every time you purchase a product through an Amazon affiliate link. Some product links in this guide are affiliate links. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast was based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Milorganite, Soil3, Territorial Seed Company, Cool Springs Press / Quarto Group and Dramm. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.
