The onset of fall doesn't have to mean the end of all of the beautiful annuals you've come to love. With a little bit of effort, you can enjoy colorful blooms on your windowsills all winter long.
Best Annuals for Overwintering
The annuals that adapt best to life indoors are the tender perennials grown in colder climates as annuals. These include popular garden annuals 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 annuals that are special to you or that have nice color or fragrance.
How to Overwinter Plants
To overwinter your annuals indoors, dig up the entire plant before your first fall frost. Cut the plants back by about a third and plant them in pots with fresh organic potting soil.
Another way to overwinter annuals is to take cuttings from your existing plants.
Take 3–5-inch cuttings from vigorously-growing plants in mid-summer. 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 when you take the cutting.
Remove any leaves from the lower half of each cutting and insert the bottom third of the stem into a pot of moist potting soil. You can add rooting hormone if you like, but most cuttings taken this way will root easily enough without it.
Place a plastic bag over the pot, supporting it with skewers, twigs, or stakes to keep the plastic up off of the plant.
Place your pot of cuttings in a bright place, but not in direct sun. In about three or four weeks, the cuttings will be rooted, and you can then remove the plastic bag and place the pot in a sunny window.
Selecting Healthy Plants or Cuttings
No matter which method you choose for overwintering, make sure you're not bringing additional problems in with your plants. Carefully inspect each plant or cutting for signs of pests or diseases, and avoid bringing in any that show problems. If you want to overwinter a plant that is showing signs of disease 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 annuals as you would any houseplant. Make sure they have plenty of light, water them when the top inch of soil is dry to the touch, and keep an eye on them for any pest or disease problems. They will not need feeding during the winter, but if you like, you can start feeding them in 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 time to acclimate to outdoor conditions. Harden them off the same way you would with any seedlings you grew indoors. This will ensure that you have a strong, healthy plant to grow in your garden, rather than one that is weak from being tossed into harsh outdoors from its warm perfect indoor conditions.