There are certain plants that won’t survive the winter outdoors. Sometimes, people buy plants that they fully intend to keep indoors through winter, like my Living Room Lemon: It goes out for summer, and comes back in for winter. (Experienced gardeners take advantage of summer to give their houseplants some air, bringing them outside for a few months and then hauling them back inside.) There are all the potted annuals you buy every year for outside; the only thing that kills them is the cold weather, so you could bring those pots inside at the end of summer. Finally, there are plants that you put in the ground that really should come inside for winter, like dahlia or begonia.
Regardless of why you’re bringing plants inside, it’s just about moving day.
When to move plants inside
In spring, we plant when the overnight temps hits 60 degrees. When they drop back to 45 degrees in fall, it’s time to move plants indoors. If there’s a freeze warning, however, that trumps consistent temperatures and you should begin emergency evacuations.
What plants to move
Plenty of people have plants they move indoors and out with the seasons, because their growing zone can’t support that kind of plant. (Tropicals and citrus plants would be a good example of these.) But you can add to that annuals like your tomato and pepper plants. Last year I covered how to prune these annuals to bring them in as potted plants for the winter. You could reasonably try to bring in any annual if you kept it in the pot—this includes herbs like basil and parsley. You can certainly try to transplant annuals from the ground into a pot to bring inside, as well, such as petunias and marigolds. In particularly cold places, gardeners dig up their dahlia, begonia, canna, elephant ear, gladiolus, and calla lily bulbs, dust them off, and store them inside for the winter. If you live someplace where winters don’t usually experience a deep freeze, you may want to risk leaving the bulbs in place.
Keep bugs out of your home
There’s a decent chance your plants made friends this summer and those friends would be only too thrilled to hitch a ride to your living room on a leaf, then take over all your indoor plants. The way to prevent this is to examine each of your plants before they head inside, and also give them a good dunk. Dunk your plant upside down in a bath of water with neem oil and castile soap, so all the leaves get coated; then, put your entire plant—pot and all—in the same bath, and hold it down until no more bubbles appear. This will help with a limited number of pests, but if you still see anything on those leaves, consider hitting your local nursery for surface treatment.
When you need a bigger pot
All that vitamin D from being outside can have a transformative effect on a plant. Yours might need a bigger pot to stretch its legs in, and now is the time to do it. Unpot the plant, untangle and unbind any roots, and examine them for health. Trim away sickly and/or moldy roots and look for pests. Dunk as above before repotting into fresh potting soil. You can also divide your plants now, or trim the leaves.
What your plants need inside
Different plants have different winter needs. For plants that you intend to continue to grow and let bloom, you need light and warmth—but not too much or direct heat—and food and water. Any blooming annuals and houseplants would be included in this group.
For plants like citrus, you need the light and warmth, but you’ll be slowing the plant growth down over winter, so it gets a dormancy period. You’ll start cutting back water and fertilizer to encourage it to slow down.
Your tomato and pepper plants are going to go into full-on dormancy, which means they need just a few hours of ambient light a day. A basement is ideal, and you’ll give them enough water and light to keep them alive, but no more, slowly waking them up come spring.
Your bulbs need darkness. Let them get dry, and then wrap them in newspaper and put them in a basement or garage where they’re safe but chilled, 60 degrees F or below.
