How to Overwinter Annual Plants Indoors

Container plants on the floor

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The onset of fall doesn't have to mean the end of all the beautiful annual plants you've come to love in your outdoor garden. With a bit of effort, you can enjoy the plants on your windowsills all winter long.

The plants that adapt best to life indoors are the tender perennials grown in cold climates as annuals because they won't survive the harsh winters. These include popular garden plants such as geraniums, coleus, wax begonias, heliotrope, and impatiens. An added benefit to overwintering these plants indoors is that not only do you get to enjoy their beauty longer, but you can also avoid having to buy them again year after year. This is a great way to keep plants that are special to you or that have nice color or fragrance.

How to Overwinter Plants

To overwinter your annuals indoors, one option is to dig up the entire plant before your first fall frost. Cut back the plant by about a third, and then plant it in a pot with fresh organic potting soil. Place the pot near a sunny window indoors.

Another way to overwinter annuals is to take cuttings from your existing plants. The following steps explain how to do this.

  1. Take a Cutting

    Take 3- to 5-inch cuttings from vigorously growing plants in midsummer. If possible, take the cuttings from non-flowering shoots. If you do have to take them from flowering shoots, cut or pinch off any blooms or buds from each cutting. This will allow the cutting to direct its energy into producing roots.

  2. Plant the Cutting

    Remove any leaves from the lower half of each cutting, and insert the bottom third of the stem into a container of moist potting soil. You can add rooting hormone if you like, but most cuttings taken this way will root without it.

  3. Cover the Cutting

    Place a plastic bag over the pot, supporting it with skewers, twigs, or stakes to keep the plastic up off of the plant.

  4. Wait for Roots

    Place your pot in a bright place but not in direct sun. In about three to four weeks, the cuttings will be rooted. Then, you can remove the plastic bag and place the pot by a sunny window.

Selecting Healthy Plants or Cuttings

No matter which method you choose for overwintering plants, make sure you're not bringing in problems with your plants. Carefully inspect each plant or cutting for signs of pests or diseases, and avoid bringing indoors any that show problems. Some common signs include discolored spots on the foliage, wilted foliage, and tiny moving insects. If you want to overwinter a plant that is showing signs of diseases or pests, quarantine it well away from the rest of your plants until you are sure you have the problem under control. 

Caring for Overwintering Annuals

Treat your overwintering plants as you would any houseplant. Make sure they have plenty of light, water them according to their species requirements, and keep an eye on them for any pest or disease problems. They typically won't need feeding during the winter. But if you like you can start feeding them in the late winter or early spring with a liquid feed, such as vermicompost tea.

When it's time to move your overwintered plants back outside, give them a chance to acclimate to outdoor conditions before keeping them there for good. After the danger of frost has passed, move the pot outdoors each day for a gradually increasing amount of hours. Do this for at least a week. Then, you can either keep your plants in their containers outside or plant them in your garden.

Article Sources
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  1. Identifying Problems of Garden Flowers. The University of Tennesee Agricultural Extension Service.