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It's getting to be time to move your plants indoors. That means more than just the houseplants that spent the summer luxuriating in our long days of warm temperatures and elevated humidity. You can also populate your house with potted annuals.
Annuals that thrive in relatively low light -- such as coleus, impatiens and browallia -- are especially good candidates for adding color to your indoor landscape. Geraniums also do well indoors, as long as you have a bright, sunny location for them.
Just don't wait for the threat of frost to make the move. While a frost probably won't kill your plants, it won't do them any good. And it can make the transition to indoor growing conditions more difficult. That's why it's best to bring your plants inside when nighttime temperatures dip into the 40s.
Making the move
Thanks to our hot weather, most potted plants put on an extraordinary amount of growth this summer, so it's a good idea to transplant them into slightly larger containers before bringing them indoors. As always, choose pots with drain holes on the bottom, so the roots of the plants won't be sitting in soggy soil.
You also should inspect plants for signs of insects or spider mites. Even if you see no sign of bugs, clean each plant thoroughly with lukewarm water before bringing it inside. Pay special attention to the stems, undersides of leaves and any area where you see fine webbing or tiny eggs.
If you have other houseplants, it's important to isolate the newcomers for two or three weeks to make sure they're not introducing any pests that could infest those other plants. Try to find a location where the plants will receive a fair amount of light during their quarantine. If you bring plants indoors and put them in a dimly lit location for several weeks, they're likely to deteriorate rapidly.
Inspect the plants again before moving them to their permanent locations. If you find bugs, spray the plants with insecticidal soap or an approved insecticide that is labeled specifically for use on plants indoors.
On the sunny side
Because there are fewer hours of daylight in fall and winter, coleus and other low-light annuals will need brighter locations indoors than they would outdoors. If you can find a spot where they'll get some direct sunlight in the morning or afternoon, they'll continue to bloom for months.
Sun-lovers such as geraniums, marigolds, hibiscus and potted herbs need even more light to bloom well.
Don't be surprised if some of the plants you bring in have a few leaves that yellow and fall. Even in bright windows, the light they'll receive indoors will be less than what they had outdoors. And reduced light translates into a reduced ability to hold on to a large number of leaves. Because houseplants usually do so well when they're outside during the summer, they typically can afford to lose some leaves.
Feed and water
With shorter days and less intense light, it's not necessary to fertilize potted annuals often in fall. Feeding once a month with a fertilizer mixed at ¼ the strength recommended on the label should do.
Water sparingly, too. Instead of keeping the soil constantly moist, allow it to dry partially between thorough waterings. (Check the moisture level by poking your finger into the soil. It should feel dry about half an inch below the surface before you water.)
Not all the annuals you bring indoors will make it through the winter. Fibrous-rooted (wax) begonias often succumb to powdery mildew after a month or two. And other plants you enjoyed all summer may gradually decline because of a lack of light. But you've little to lose, so why not bring a few potted plants inside and enjoy them as long as you can?
Deb Brown is a garden writer and former extension horticulturist with the University of Minnesota. To ask her a gardening question, call 612-673-7793 and leave a message. She will answer questions in this column only.