The end of the gardening season does not have to mean the end of your container plants. Although most will not survive the winter in freezing climates, they can be brought indoors as houseplants. Once the nighttime temperatures start to get cooler, it's time to think about bringing tender plants indoors, and that includes any vacationing houseplants that you brought outdoors in the spring. If your plants aren't good candidates for indoor life, there are other good alternatives.
Successfully overwintering plants indoors starts with the choice of plants. Not all plants can survive indoor growing conditions, especially if your home has limited light, warmth, or humidity. Since there is a good chance there are fewer sunny spots inside your house than in your yard, you will have to make some choices about what's worth keeping and if you are going to be able to give them the care they need.
Although it's tempting to want to move every plant you have been growing in a container indoors for the winter, it is also impractical. You and the plants will fare much better if you run through the following checklist and keep only the plants that meet these criteria.
- Keep only healthy plants. If something has been struggling all summer under the best of conditions, it is not going to improve indoors. Time to face the compost.
- Never bring in a plant with pests or diseases. Don't try to convince yourself that you'll quarantine the plant until it's been coaxed back to health. Problems spread more quickly among indoor plants than in the garden. There are no natural predators of insects in the house and indoor conditions can be ideal for a disease to spread. Check all plants thoroughly for any signs of problems, before you bring them indoors.
- Give priority to your favorite plants, the ones you've been coddling for years, like a bay tree, anything you've trained into a standard, and sentimental favorites. Of course, expensive splurges are worth the effort, too, if you have the room.
- If the plant would look good as a houseplant, bring it in and use it as one. Many people have the light to successfully grow winter geraniums, fuchsia, begonias, and even passion flower, in full bloom. They may not look as lush as they would outdoors, but it's still nice to have something blooming in winter and they'll be ready to start blooming outdoors early in the spring.
- If you have the room, consider bringing in some small pepper or tomato plants. These are actually tropical perennials and given enough light, will continue to produce fruits all winter. Tomatoes need a large pot. You'll have more success growing a compact, patio variety. Cherry tomatoes and small-fruited peppers like chilies or cherry varieties will fruit easiest and give you a higher yield. Just keep in mind that there are no insects or gentle breezes indoors to pollinate your plants. That will be up to you.
Some tender perennials like a period of dormancy in winter. You can overwinter potted lavender and rosemary in your garage or basement. If the temperature doesn't go below 20 degrees Fahrenheit or above 40, they won't freeze but will stay dormant. Just don't let the pots dry out or stay overly wet. Water them only when the soil becomes dry a couple of inches below the surface and allow any excess to drain out.
Be realistic about space and available light. You can always start cuttings. Cuttings take up much less space and may even do better than established plants because they won't suffer the shock of adapting to new growing conditions. The small plants will have time to develop their roots during winter and will be ready to be moved out into the garden and start growing early in the spring.
Once you've decided which plants will make the cut, give your outdoor plants time to acclimate to being houseplants. Bring them indoors while the windows are still open and the temperature indoors is about the same as outside. They'll adjust to the change in temperature and humidity more easily if the change is gradual, rather than waiting until a frost is expected and then bringing the plants into a dry, heated home.
Dormancy: A Key to Winter Survival. University of New Hampshire Cooperative Extension Website