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When to Bring Plants Inside

True annuals and plants that we grow as annuals (considered tender perennials in southern regions) can not survive cold winter temperatures. But there’s no need to say farewell to these plants forever! Many “annuals” can be brought inside, even tender plants that need a winter dormancy period. These should ideally come indoors before nighttime temperatures dip below 45°F (7°C). As fall approaches and nighttime temperatures reach about 50°F (10°C), start bringing the plants inside for the winter.

Most tropical plants will suffer damage at temperatures below 40°F (4°C), a few even below 50°F. You will need to act well before any actual frost or freeze to acclimate them.

Where to Put Your Plants

Even though we have a greenhouse attached to the house that gets plenty of sun, and the temperature there doesn’t usually drop below 45°F, I still have difficulty finding room for everything. Luckily, many of these plants would undergo a dry period in their native lands and don’t mind being shoved under a bench to rest.
 

If you don’t have a greenhouse and have a lot of plants that need high humidity, think about creating a shelf or area to group these plants. Some folks mist their indoor plants, and—while this does help—it only lasts for a short period. A better long-term solution is using a pebble tray under your plants. Line the trays with waterproof material, add a layer of gravel, and place the pots on top. Keep the gravel moist. If you have hanging plants, perhaps you want to install some ceiling hooks. It’s also a good idea to clean your windows—inside and out—to ensure plants get adequate light this winter. 

Which Plants to Bring Inside

You may need to decide what’s worth bringing indoors. Which plants are your keepsakes? Which are the most expensive to replace? Also, keep only the healthy plants, not those with disease or pest problems. Your indoor lighting will be crucial, too. In winter, even a west- or south-facing glassed area has only the light intensity of a shady area in the summer. 

Plants that can be brought inside fall into two groups:

1. Plants that require a winter dormancy period.
2. Plants that can remain actively growing through the winter months. 

Plants Requiring Winter Dormancy

Some tender bulbs require a “dormant” time in a cool place where the temperature is still well above freezing. Many of these bulbs are expensive and worth overwintering. Examples of tender bulbs are:

• Caladiums
• Calla lilies
• Cannas
• Dahlias
• Elephant ears
• Gladiolus
• Tuber roses

For tender bulbs in pots, stop watering them, cut off the dying foliage, and tuck them away in a dark, cool location. Check the soil moisture periodically. 

For tender bulbs in the ground, dig them up and cut the foliage back. Brush off as much soil from the bulb as possible by hand. Place them in a warm, dry area for 7 to 14 days to dry. This removes excess moisture. Pack them loosely in a cardboard box or open container, separated by shredded newspaper or dry peat moss. Tuck away in a cold, dark place.  Pot them up in the spring about a month before you want to put them outside for a jump on the season.

Read my post on how to store tender bulbs for winter.

Plants That Keep Growing in Winter

Many of my annuals, herbs, and tropical plants will keep growing through the winter, and some will even reward me with a bloom or two. These will need a prime spot in the sun, but they don’t seem to mind the cool temperatures.

• Coleus
• Fibrous begonia
• Fuchsia
• Geranium (if given plenty of light)
• Hibiscus
• Cymbidium
• Amaryllis
• Agapanthus
• Iresine
• Mandevilla
• Rosemary

It’s best to acclimate the plant to a lower lighting level for a few days before moving them fully indoors. For example, move a plant outdoors in full sun to a shadier area. If your plants have been used to bright light, try to put them in similar light indoors, like a south-facing window or under plant lights on a timer for 16 hours a day. Do not worry about leaf drop as the plants adjust to interior conditions; they will recover.

Also, if your plant needs some pruning to temporarily reduce its size, prune it before bringing it inside.

Fuchsia are a bit of a bug magnet, so I cut off their leaves and water the roots just enough to keep them living. In spring, they will start up again with fresh new growth and be in bud when it is time to go back outside.

We keep the geraniums blooming all winter as well, but if you lack a sunny place for them, you can let them go dormant by cutting back by about half, putting a bag over the top, and watering only if they begin to shrivel. Some people even remove them from their pots and hang the bare-root plants upside-down in a dark, cool place, spraying them with water occasionally to keep them from shriveling up. Soak the bare roots in the spring for several hours to rehydrate them, and then repot the plants.

Get Rid of Pests

To ensure I’m not bringing in any unwanted visitors, I rinse all the leaves with a vigorous spray of water and check the pots all over, especially under the rim, for bugs, slugs, cocoons, and egg masses.

When they are observed, treat an infestation with insecticidal soap or other insecticide labeled for these pests. I try to spray all the leaves down with a soapy spray made from 1 teaspoon of non-detergent soap (I use Dr. Bronner’s liquid lavender mostly because it smells so good) mixed with water in a 1 quart spray bottle. Spider mites have a life cycle of 7 to 10 days, so weekly spraying usually halts their growth. If I notice whiteflies, I’ll put up some yellow sticky cards to catch them. Don’t forget to spray under the lip of the container and the bottom of the container, where insects can hide.

Indoor Plant Care Tips

Don’t overwater! This is the most common cause of death for indoor plants, which don’t need much water in wintertime. Let the top 1/2 inch of the soil get dry to the touch before watering again. If in doubt, don’t water. Water succulents even less often when the soil has been dry for several days. Don’t water in cloudy or rainy weather, as plants won’t get sufficient light indoors to dry out. 

Plants require little, if any, fertilizer during the winter months due to lower light intensity levels. Fertilize in the spring, just before new growth begins.

You can save yourself a bundle by overwintering some expensive tropical plants. If you have more plants than window space allows, offer them to a gardening friend!

Taking Cuttings

Just to be on the safe side, I also take cuttings of some of my favorites—like iresine, begonias, geraniums, impatiens, and coleus. All will root easily in water and make attractive houseplants.

Cuttings are a wonderful and inexpensive way to create more plants if you lack space to store pots over the winter. 

To take a cutting:

1. Choose healthy shoots and trim them about 2 to 3 inches below a leaf node. Remove any lower leaves and flower buds. 
2. Insert the cutting into a moistened rooting medium—such as coarse sand, vermiculite, or sterile potting mix (which typically contains both peat and perlite). Also, insert at least one leaf node below the medium surface. Tip: It is optional, but consider dipping the cutting in a rooting hormone prior to planting. It may help the odds of success.
3. Place the cutting in bright, indirect light. Maintain an even moisture level. Covering the container with a plastic hood or clear bag will reduce overall moisture loss.

Rooting typically takes 1 to 3 weeks, depending on the plant. Once the roots are well-developed, you can transplant to a larger container.

Moving Plants Back Outside in Spring

In spring, your plants will start to send up new growth, and you can drag those pots back into the sunlight and resume watering them. If needed, I will give them a new container with fresh potting mix.

To be on the safe side, wait until after the last frost to move them back outside. 

A Few More Winterizing Tips

• Plastic and wooden containers can be left outside for the winter. Terracotta clay containers, however, may crack and should be brought inside.
• Before the temperature drops to freezing (32°F/0°C), disconnect garden hoses from any outdoor faucets. Fully drain the hoses and screw the ends together to keep out any insects and debris. Then, store them under the deck or in the garage.
• Good tools are expensive! Spend the time to take care of them properly. Clean tools with a wire brush and sharpen the surfaces. Apply a light coat of oil or product such as WD-40 to metal surfaces. Wipe wooden handles with an all-purpose cleaner and apply a light coating of wood preservative. See how to care for and sharpen garden tools.

Read more of my tips on fall garden clean-up.

Here is more advice on preparing your garden for winter—from vegetable beds to rose bushes to trees and shrubs!