It would be a shame, not to mention a waste of good money, to let winter’s cold kill some of your favorite outdoor plants. Luckily, many plants can make it through the winter if they are moved inside and treated properly. Before fall’s first frost, consider bringing these plants indoors for the colder months. Here’s what you need to know…

Choose good candidates. Not all plants will make it through the winter, whether they’re outside or in. Good candidates include plants that are long-lived but not cold-hardy enough to survive outdoors such as geraniums…mint…chives…calla lilies…gladioli…dahlias…and begonias. Popular annuals such as pansies, marigolds, zinnias, impatiens, petunias, parsley and rosemary are not worth trying to save. Pull them up when they’re past their prime, and add their remains to your compost pile.

Find a good indoor spot. For the colder months, most plants are essentially hibernating. You’re not moving them indoors to alter that natural tendency or force a continuing summer. Bringing them in keeps them safe until they can return to outdoor life next spring. 

You will need to store them in a cool, dark place—choose a shed, garage or cool basement. Their indoor location should remain above 32°F so that nothing freezes. The ideal temperature is between 40°F and 50°F. Make sure plants are not placed near a clothes dryer, ­water heater or furnace, as the heat can dry out and kill the plants.

Making the move. Follow these steps for a successful transplant…

Step #1: Prepare your plant for the move. Act once you see that a plant is past its peak but before the first frost comes along and kills it. In early to midautumn, start by removing dead leaves and stalks, including those that have slumped or been matted down on the ground around the plant’s base. Completely clear this debris from your garden bed. Why that matters: Pests and disease often make a home for themselves in the plant debris. If you don’t dispose of the debris, you run the risk of bringing pests inside with your plants. 

Step #2: Shorten stems by one-third to one-half. You can do this without worrying that you are harming the plant. Use sharp scissors and/or pruning shears to make a clean cut. Work gently, since yanking off pieces can harm a plant’s crown or root system. 

Step #3: Choose an optimal day for the transfer. Best time: An overcast or drizzly day will be less stressful for the plant. Barring that, do your gardening early in the morning before the heat of the day reaches its peak. Why that matters: Plants are less susceptible to drying out in cool, wet weather. 

Step #4: Prepare the winter pot. Place a large pot with drainage holes in the bottom next to the in-ground plant. Sprinkle some sterile potting mix into the waiting pot. “Sterile” is desirable because you won’t risk adding any potential plant pests or ­diseases.

Step #5: Dig up your choices with a sharp trowel or shovel. Important: Just because a plant’s growth is slowing down for the year doesn’t mean that you can handle it roughly. Be gentle! Try to get most—if not all—of the plant’s root system. A good rule of thumb is to dig two or so inches beyond the point on the ground where water drips off the widest part of the plant.

Handle the plant by the crown (more or less the ground-level point where the main stem emerges), not the leaves, and shake off the heavier soil clumps. Gently set your plant into the winter pot. Add more sterile potting-soil mix to fill in the gaps around the plant. 

Step #6: Give your transplanted plant plenty of water—water it until the water runs out the bottom. Then add more potting mix until it is right up to the plant’s crown—that is, to the level the garden soil was at when the plant was growing in the ground outside. 

Step #7: Let the potted plant dry out for a day or two in a shady or sheltered outdoor spot. Do not water the plant again prior to storage.

Step #8: Place the pots in your preferred location. This should be out of the way of foot traffic from people and pets but still accessible to you. Check the soil once a week by plunging a finger into the pot about an inch deep. If it’s dry, add some water—just enough to dampen but not drench the soil mix. Never fertilize during the winter months.

Note: Some plants—such as geraniums, some that grow from tubers such as dahlias, and some that grow from corms (underground plant stems) such as gladioli—can be stored bare and do not need pots. That is because they use their tuberous roots to store food and energy for next season’s growth. Exception: Tuberous begonias and calla lilies tend to have fragile rootstocks, so store them potted. 

To Store without a Pot…

Gently clean the plant after digging it up, taking care not to break off any white roots. Snip off all dead and withered top growth. The stems will have dried out by the fall, so there should be little to none left. Store your plant in a mesh bag (to avoid rot) or a box of sand, wood shavings, vermiculite or even recycled packing peanuts. Tip: You can loosely wrap dahlia rootstocks in newspaper, taping the entire packet closed. Unwrap in February to check on them, then rewrap and sprinkle the newspaper with a little water so that they won’t completely dry out. Over the winter, watch for signs of rot in plants that were stored bare (such as soft or mushy spots, a bad smell or mold). Toss out the tainted ones. 

Back to the Garden at Last

When longer and warmer days return in early spring, check on your plants ­every few days. Start watering the potted plants, gradually increasing frequency and amount. You can move them to a brighter but still-sheltered place, such as a garage. After a few weeks of this regimen, you may give a little diluted fertilizer to encourage returning signs of life. Growth will naturally resume when conditions are right. 

If some of your plants aren’t showing any activity but warm, frost-free weather has returned, you may move them outside—staging them in a protected area for a week or two. The ideal outdoor staging area is sheltered…out of the wind…and not in full sun—a porch or gazebo, for example. Start watering them out there. They should be inspired to wake up.

Note: Some plants seem to have an internal clock even if they are not getting clues from the weather. If you see signs of life on ones that have been stored naked—little whitish or pink growing points, or buds or “eyes” on rootstocks—move them into a pot with potting mix. But don’t move them outside if it’s still too cold. When danger of frost is past and the ground is not too muddy, you can replant them in garden ground—growing tips pointed up. 

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