How to Prepare Outdoor Plants to Come Inside

As summer comes to an end, and cooler temperatures arrive, gardeners start to bring their outdoor plants inside. Most of them will be indoor plants that were allowed to bask in the summer sun for a few months, but sometimes you can extend the life of a beloved potted annual, herb, or tropical plant by bringing them inside.

Not all plants will overwinter well, but there’s no harm in trying. This article will go over how to prepare outdoor plants to come inside, and discuss some of the varieties that you can take a chance on.

Make a List (and Check it Twice)

September is a good time to take stock of what outdoor plants you might want to bring inside, and start to make a plan. Any indoor houseplants that were transitioned outside will need to come back in at some point, but maybe you also bought a few others this summer and wonder if they can overwinter, as well.

Make a list of what plants you want to transition inside and group them according to needs. Some will have to come in sooner than others, but all of them will need to be brought in well before frost is expected.

Tropical Plants

Popular tropical plants that gardeners purchase to adorn patios and decks will die once cooler temperatures arrive. It can be costly to buy them each spring only to lose them just before fall arrives.

Majesty palms, Boston ferns, mandevilla, hibiscus, Dipladenia, oleander, banana trees, birds of paradise, crotons, ferns, and palms are all commonly sold in nurseries over the summer, and with some care, they can make it through harsh winters.

How you go about doing it, depends on the plant, and your home’s light conditions. Hibiscus, bird of paradise, mandevilla, crotons, and Dipladenia will stay vivid and even bloom if they are placed near a large, bright, sunny window.

Hibiscus, oleander, bougainvillea, and banana trees can also be forced into dormancy by moving them to a dark, cool place like a basement or garage, and then reducing water.

Majesty palms and Boston ferns don’t need full sun like the others, so they can be placed in medium, or bright, indirect light, and will do just fine over the winter if you have the space.

Check Frost and Tender Dates

Once you’ve decided what plants are making the trek, find out what their cold tolerance is. The majority of tropical plants (which include most varieties of indoor plants), will not tolerate temperatures lower than 50 degrees F, though some can handle a night or two.

They will die, however, if temps drop to 32 degrees F, which is freezing point. If weather stays nice through October, and there are a few cooler nights, they tend to be fine, however, it’s best to transition them inside sooner than that.

Once temperatures consistently drop below 65 degrees F, you should start bringing them in, as you don’t want to stress them out (even if they still look pretty on your patio).

Annuals and Tender Perennials

Most of the annuals you buy in the summer are actually tender perennials, meaning they don’t die at the end of summer in warmer climates. True annuals only have a short lifespan, no matter where they are grown, whereas you can take a chance on growing tender perennials inside.

Geraniums, lantana, sweet potato vine, fuchsias, coleus, and begonias are some common plants sold as annuals that can be over-wintered in various ways. They usually need the full sun and hot heat of summer to thrive, so mimicking conditions indoors is tricky unless you are blessed with greenhouse-like conditions, and large, south-west facing windows.

Most people don’t have this in their house, or if they do, the space is limited. Cuttings are a great way to keep the plant alive, while reducing the amount of space they take up, as you are only growing a portion of the plant in a smaller pot.

The other option is to force them into dormancy by keeping them in a dark, cool place with reduced watering. An unheated garage or shed may work if you don't experience heavy frost for long periods.

If you have this kind of space, you can try keeping plants like salvia, geraniums, dusty Miller, sage, rosemary, and pansies alive. They’ll have the best chance if temperatures are between 45 F and 60 F, but some are even more cold-tolerant.

True annuals aren’t worth the bother because they aren’t meant to last longer than a season. Don’t try to overwinter zinnias, marigolds, sunflowers, amaranth, and cosmos, for example, and if you want to buy plants to overwinter next year, don’t always rely on the nursery tag to tell you which ones are true annuals.

Clean Them Up

Any plant that you want to keep alive, whether it’s brought inside your home or put in a garage, will benefit from a proper clean-up. Prune and dead-head any spent flowers, and cut back any plants that benefit from a haircut.

Most indoor plants don't grow and flower in such a way that they will have a lot of foliage to prune, but you can wipe their leaves with a damp cloth to remove dirt and dust. Tender perennials and annuals will benefit from a more thorough tidying.

For all plants, clean out any leaves and debris around the top of the soil, and if you are bringing a pot inside, clean it with soap and water.

Treat for Bugs

Before you bring any plants inside, you need to begin the process of de-bugging them, as it takes about two weeks. The majority of outdoor plants will have some form of travelers on their leaves, or in the soil, and while most are benign, others will wreak havoc inside.

Start by giving your plants a good, hard spray with the hose (if the plant isn’t too delicate). This is a great way to remove most of the pests without killing the beneficial ones. Spray the entire plant, including both sides of leaves, near burgeoning blooms, and along stems. (Make sure the pot has drainage!)

Water the soil thoroughly to drown anything, and to give your plant a good drink before treating with any sprays or soaps. It’s best to water before you treat for bugs so you don't wash off the spray.

After a wash, you can treat your plants with insecticidal soap. This will kill any leftover pests like aphids, spider mites, and any other soft-bodied insects. Spray the whole plant and the soil, as well, thoroughly soaking it. Let it dry and keep the plant outside for one week, then apply the insecticidal soap a second time.

If you can, quarantine your outdoor plants, even after being treated for pests. If you have a sun-room, patio, or another closed off space, put them there for another week and do an inspection.

Sun-rooms and patios can also be a good place to transition outdoor plants as it reduces sunlight just enough to help them make the move indoors, and provides coverage from frost.

If a plant looks unhealthy at any point during the treatment for pests, or the transition, best not to bring them inside for a number of reasons: you don’t want to spread whatever disease or infestation it might have, and it may not be worth the effort, time, and space to bring it back to life, especially if it’s a tender perennial that will struggle over the winter, anyway.

Allow Them to Acclimate

As you are de-bugging, slowly transition your plants away from full sun. As fall approaches, daily sunlight naturally wanes, but even the sunniest of homes have lower light than the outdoors.

To help your plant transition to lower light conditions, move them gradually to a spot outside that receives part sun, or move into a sun-room or other outdoor space that's sheltered. These rooms can allow your plants to stay in conditions that are relatively similar to outdoors, while protecting them from frost longer.

Spend approximately two weeks transitioning them before bringing them inside, or allow them to stay semi-outdoors longer in a sun-room or covered space.

Prepare the Indoors

While plants are being transitioned and "de-bugged" prepare the indoor space for them. Clean windows so they bring in more light, and to give the space a fresh look. This also helps remove dust and old webs that pests can cling onto.

Vacuum the floor and surrounding furniture thoroughly, as well. Clean floors with a disinfectant, and remove any mold that can sometimes get trapped in window panes.

You can also change light bulbs to full spectrum to get the optimum amount of light from fixtures. Install grow lights in areas where you think plants will need it. Plan your "plant-o-gram" and set up tables, stools, and hooks for hanging baskets in spaces according to plant needs.

Lighting

You'll need to find similar lighting situations that your plants had when they were outside, though, very few homes can completely replicate the conditions of summer. Note: some plants that like full sun outside may suffer from burnt foliage if set in a hot window with direct light.

Keep in mind that direct indoor light is still less intense than outdoor sun, so you may need to add supplemental lighting for certain species, especially tender perennials, or for plants in rooms that aren't south-west facing.

Temperature

Some plants are less fussy than others, but none of them will be happy with any extreme temperature fluctuations, or cold drafts. Set them away from vents and air registers, as hot air isn't preferred, either. Keep them away from exterior doors or windows that aren't sealed.

Indoor temperatures should remain consistent between 68 and 75 degrees F. Sheer curtains can help with any intense heat and sunlight, though better to move plants away from a hot window than reduce sunlight.

Humidity

Your indoor plants will all appreciate extra humidity during the dry, winter months. You won’t need to worry when windows are still open and the furnace isn’t running, but once the heat is on every day, (especially forced air gas heating), be ready to add some moisture to the air.

A humidifier is the easiest way to help your plants, so make sure you get the right size for the space. Grouping your plants together allows them to contain moisture around their leaves and soil.

Pebble trays and misting can also help, but be careful with spraying plants that are susceptible to fungus and leaf spots.

Watering Needs

Indoor plants will naturally need less water than when they were outside in the full sun or heat of summer, but you want to gradually reduce watering. Some plants will continue to bloom and grow, even in the early fall, so watering should be on a case-by-case basis.

Be careful during this period not to over, or under water them. For example, some citrus plants prefer consistently moist soil, whereas succulents like a long dry out period.

Most plants go semi-dormant by the time winter comes around, which is when they require the least amount of water. In general, continue to water plants when the top inch or two of the soil is dry, or according to their needs.

Don’t Transplant (Unless Necessary)

Transplanting and re-potting can stress out a plant. When you are transitioning plants from outdoors to indoors, they are already going through a mild amount of stress. Re-potting at this time would only increase trauma, especially for sensitive root systems.

There are always exceptions to the rules, and most plants will tolerate re-potting depending on the reason for it, and how you do it.

Don’t transplant anything that is still flowering. Wait for the plant to slow down it’s growth naturally, perhaps when you are acclimating them to shadier spots, as this signals the plant to prepare for a dormant stage.

Don’t re-pot just for the sake of it. Only transplant anything that has become extremely root bound, or something that was in the ground that you want to move into a pot. You may also re-pot if you want to change out the soil.

Spring is the best time to re-pot the majority of indoor plants, as they naturally want to start growing at this time and will happily fill in a larger pot. It's better if you can wait until this time to re-pot anything, as it will save the plant from any added stress.

Feed Them Accordingly

Plants have different needs, and just like re-potting sensitivities, some plants are heavier feeders than others. For most indoor plants, however, you can approach fertilizing similarly, and add or subtract amounts as needed.

Fertilizing schedules also depend on the climate they are in. If you live in an area with cold, dark winters, then you want to start tapering off feeding mid-to-late summer. You can continue to feed during the early fall, but reduce the amount in half, finally ceasing feeding altogether during the winter.

For climates that aren’t as harsh, feeding may still be reduced, but not stopped altogether. The science is particular to plant profiles, as well as the growing season.

Some gardeners suggest fertilizing when they first come inside. This can help prevent leaf drop and give them enough energy to get through the darker months ahead. Again, individual plants have specific fertilizing needs, so the best thing to do is research each and every one to see what kind of feeding they prefer, and when.

If plants are being sent into dormancy, normally you don’t want to feed them, but again, check the plant profile to see if they could benefit from specific nutrients before they go to sleep.

Don’t Move Them

It’s especially important for the first few weeks that you allow your plants to transition fully to their new home, even if they’ve been there before. Try not to move plants around to different locations.

It can be hard not to move things around if you have new plants and are trying to find space, but if you do your planning beforehand, you won't have to worry about this.

Of course, there will be some alterations as the season goes on, as some plants will want more or less light, but the less shuffling around, the better.

Proper planning will be extremely beneficial when moving and preparing outdoor plants to come inside. Be practical with your choices, and thorough when it comes to debugging and other preparations. This will give you the best chance at having happy, healthy plants all season long.