When frost threatens, it's time to move many of your outside plants indoors. Many tender bulbs, annuals, herbs, and tropical plants will only survive the winter inside. Here's advice on which plants to bring indoors this fall and how to winterize plants and pots.
When to Bring Plants Inside
True annuals and plants that we grow as annuals (considered tender perennials in southern regions) cannot 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 night 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°. You will need to act well in advance of any actual frost or freeze to acclimate them.
Where to Put Plants
Even though we have a greenhouse attached to the house that gets plenty of sun and the temperature in there doesn't usually drop below 45°F, I still have a hard time finding room for everything. Luckily for me, many of these plants would undergo a dry period in their native lands and don't mind being shoved under a bench to rest.
The greenhouse fills up fast, especially when the pots are big.
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 together. Some folks mist their indoor plants and—while this does help—it only lasts for a short period. A better long-term solution is the use of 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—both inside and out—to ensure that plants will get adequate light this winter.
Which Plants To Bring Inside
You may need to make some choices about what's worth keeping and bringing indoors. Which plants are your keepsakes? Which are the most expensive to replace? Also, keep only the healthy plants and not plants with disease or pest problems. Your indoor lighting will be important, too. In winter, even a west or south facing glassed area has only the winter light intensity of a shady area in the summer.
Plants which can be brought inside fall into two groups:
Plants that require a winter dormancy period.
Plants that can remain actively growing through the winter months.
This canna will get a winter rest when it is cut back and dried out.
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 over wintering. Examples of tender bulbs are:
For tender bulbs in pots, just stop watering them, cut off the dying foliage, and tuck them away in a dark, cool, spot. 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.
This Bolivian begonia will keep blossoming for a few weeks indoors before it drops its leaves for the winter. We have kept the tubers going, in the same pot, for several years.
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.
Geranium (if given plenty of light)
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 that’s in full sun outdoors to a shadier area outside. If your plants have been used to bright light, try to put them in similar light indoors, like a south window or under plant lights on a timer for 16 hours a day. Do not be too worried 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.
This hibiscus will sulk and drop its leaves eventually, but perks right back up in spring.
The 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.
The cymbidium produces its first flower stalk as soon as we bring it in and will bloom for much of the winter.
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 pot and hang the bare-root plants upside-down in a dark, cool place, spraying 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.
If a combination worked well and you want to repeat it again next year, take some cuttings.
Get Rid of Pests
To make sure I'm not bringing in any unwanted visitors, I rinse all the leaves down with a vigorous spray of water and check the pots all over, especially under the rim, for bugs, slugs, cocoons, and egg masses.
As soon as they are observed, treat an infestation with an insecticidal soap or other insecticide labeled for these pests. I try to spray all the leaves down with a soapy spray made from 1 tsp. of non-detergent soap (I use Dr. Bronner's liquid lavender mostly because it smells so good) mixed with water in a 1 qt. spray bottle. Spider mites have a 7 to 10 day life cycle 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 as well as the bottom of the container where insects can hide.
Indoor Plant Care Tips
Don't over-water! This is the most common cause of death for indoor plants, which really 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 of your expensive tropical plants. If you have more plants than window space allows, offer them to a gardening friend!
This pink mandevilla was given to me because it was too large for my friend to fit on a windowsill and she could not bear to throw it out.
Just to be on the safe side, I also take cuttings of some of my favorites—like the iresine, begonias, geraniums, impatiens, and coleus. All will root easily in water and make attractive houseplants.
If you lack space to store pots over the winter, cuttings are a wonderful and inexpensive way to create more plants.
To take a cutting:
Choose healthy shoots and trim them back about 2 to 3 inches just below a leaf node. Remove any lower leaves and flower buds.
Insert the cutting in a moisted 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.
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 one to three 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 pot with fresh soil.
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 coat of light 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.