How to Overwinter Potted Petunias in 9 Steps

Why let petunias die in autumn? If you have them in hanging baskets, containers, or small pots, learn to overwinter them indoors or outdoors with these 9 easy steps. Join backyard grower Jerad Bryant and learn what your tender perennials need to survive the cold season.

Written by Jerad Bryant Horticulture review by Sarah Jay Last updated: September 27, 2024 | 7 min read

A shot of flower outdoors that is one example of a method to overwinter potted petunias

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Why overwinter potted petunias? Maybe you found the perfect variety and want to keep it for next year, or you’d like to experiment and use outdoor plants as indoor ones. No matter your reasons, these steps ensure they survive the winter so you can enjoy their blooms next spring.

Most petunias, including similar-looking calibrachoas, are short-lived frost-tender perennials. This means they live for two to three years in frost-free zones. Trick your plants by bringing them indoors in cold zones or by having them enter dormancy in a garage or greenhouse. We’ll learn how to accomplish both these methods and see which is easier for keeping your plants alive.

These steps work well for overwintering potted petunias or calibrachoas and their hybrids. Use this guide in the autumn to trick your plants into blooming for another year or two. You’ll save money next spring on new potted plants, and your current one will be ready for the outdoors before most nurseries have any available.

Here are the nine easy steps to overwinter potted petunias without further ado.

Step 1: Stop Applying Fertilizer

A focused shot of a person wearing a white shirt with blue-green gloves fertilizing a red flowers in a pot outdoors — Apply fertilizer if you plan to bloom the flowers indoors.

Plants need fewer nutrients as they die back and enter dormancy. If you keep adding fertilizer to the soil, it can trick them into growing excess leaves and stems at the expense of healthy roots. You’ll want to cease fertilizing a month or two before your first fall frost as temperatures lower and tree leaves begin changing color.

You may keep applying fertilizer if you plan on forcing your petunia to continue blooming indoors. This perennial naturally dies back and enters dormancy during cool winter periods—it prefers to rest so it can bloom prolifically next spring. You may force it to flower indoors by applying fertilizer regularly and by giving your potted plant at least 10 hours of bright light daily.

Otherwise, plan on stopping fertilizer applications in late summer or early fall. Petunias need regular fertilizing to bloom their best—you’ll notice they’ll stop blooming and produce fewer leaves and stems when you stop giving them nutrients. This is perfect, as we want them to enter dormancy so they have the highest chances of survival.

Step 2: Trim Stems Back

A close-up shot of a person using scissors to trim or deadhead wilted pink flowers in a garden or outdoor area. — Trim the flowers to reduce flowering and excess growth of leaves.

Whether you’re keeping your potted petunias indoors or out, you’ll want to trim them to encourage less flowering and excess leafy growth. Start by deadheading all the flowers, including newly forming buds. It may be hard to prune away the flowers, but know that they’ll come back tenfold during the growing season if you prune them now.

After deadheading all spent flowers, trim back any leggy stems. This forces your plant to start sucking in nutrients from its leaves so that it can focus on growing roots. You want more root growth than top growth indoors during wintertime, as this is what petunias do naturally in their native range.

While trimming, look for any dead or damaged foliage and stems. Prune these off readily to give your container specimen a clean, fresh look. It’ll also prevent future diseases and pests that like to overwinter on dead plant debris.

Step 3: Inspect Petunias For Pests or Diseases

A focused shot of a pink flower that is infested with a colony of aphids in a bright sunlit area outdoors — You’ll need to get rid of the bugs or infected plant parts immediately.

After trimming your plants, you may notice insect pests or diseases flourishing in the pot. You’ll want to get rid of these pathogens and bugs before overwintering your petunias indoors. Pests and diseases thrive in our homes, as they lack the beneficial bugs and microbes that keep bad ones in check.

In the outdoors, cold winter temperatures kill most pests, and your petunia’s winter dormancy protects it from pathogens. If you notice diseases persisting on your outdoor plants in the dormant months, use organic treatments to return them to healthy conditions. Trim off any infected foliage, and apply organic sprays if needed.

Pests are a little easier to deal with since you simply need to remove them. Aphids, whiteflies, thrips, and spider mites may be munching on your potted petunias or calibrachoas. Use strong streams of water daily to knock them off the stems and leaves.

If they persist longer than a week with regular water spraying, apply an organic pesticide like neem oil or horticultural soap. They’ll kill the bugs and coat your plants with a protective layer, thwarting future infestations. Be sure to apply these chemicals in the morning or afternoon away from wildflowers to prevent harming beneficial bees, birds, and wildlife.

Step 4: Leave Them Outdoors In Warm Climates

A shot of three different colored flowers hanging outdoors in a warm bright sunlit, rustic farm area. — Keep the flowers outdoors at hardiness zones 10 through 11.

If you live in zones 10 or 11, you’re in luck! Petunias readily overwinter in these zones without issue. They’ll enter dormancy and stop actively growing, then resume heavy growth as temperatures warm in winter and spring. If you’re growing calibrachoas or mission bells, you can keep them outdoors in pots from hardiness zones 9 through 11.

Move your containers under cover so you have control over how much moisture they receive. Excess fall and winter rainfall may cause root rot in dormant petunias, turning your beloved perennials into mushy messes. Under a porch or patio, you can moderate how much water they receive to match their needs.

If you live in these hardiness zones and have occasional frosts, your petunias may suffer. Bring them indoors or under cover if you have an extreme frost forecast with temperatures below 40°F (4°C). Safely return them outdoors once temperatures warm up.

Step 5: Find An Ideal Location Indoors

A focused shot of pink flowers in a small pot indoors, near a window on a wooden surface with gardening tools on the right side. — Once indoors, you can either let the flowers into dormancy or make them flower continuously.

If you live below hardiness zone 9 or 10, like myself, you’ll want to bring your containers indoors during cold months. You have two options for overwintering potted petunias—let them enter dormancy or force them to continue flowering. Different homes have various conditions, so use the method that works best for your space.

Dormant petunias and calibrachoas need cool temperatures and bright indirect light to continue thriving. Avoid putting them near heaters or warm drafts, as the heat confuses them. A bright windowsill that stays cool, between 40-65°F (4-18°C), is ideal. Temperatures lower or higher than this range will cause petunias to freeze or to prematurely exit dormancy.

If you’d like flowers throughout the winter, try keeping your petunias in bloom! They’ll need 10 hours of bright light daily and temperatures between 65-80°F (18-27°C) to stay active. If you live where winter days are short with few hours of daylight, use grow lights indoors to extend the season. Deadhead spent flowers often and trim leggy stems to keep your plant bushy, prolific, and healthy.

Step 6: Water When The Soil Dries Out

A shot of a person holding a yellow container, and using it to pour water on multi-colored flowers. — Water the soil if it’s dry all the way through.

Dormant petunias need much less water than actively growing ones. If you continue watering their containers with the same amount, they’ll drown and rot. You’ll want to adapt your watering schedule to match their needs.

The best way to know when to water is to finger-test it. Simply stick your finger in the dirt and see if you can feel moisture at the bottom. If it’s dry all the way through, you’ll want to water your petunias well. If it’s dry on top but wet below, hold off on watering until more of the root zone dries out.

Actively blooming plants need more water than dormant ones. They still appreciate irrigation after their soil dries out, which means you can use the finger test with them, too. Check two inches below the surface to see how moist the soil is, and water accordingly.

Step 7: Monitor Plants For Changes

A focused shot of a person spraying organic neem oil to repel pests on white-pink flowers on a pot — Monitor the flowers and make sure there are no pests on the leaves or stems.

The winter months are especially tough on insects and small critters. They often try to find new homes in our houses where they can stay warm all season long. Continuously monitor your potted petunias to make sure none of these pests establish themselves in the leaves or stems. Squish, spray, or prune off the pests as you see them to prevent further infestations.

Another common petunia issue in the winter is leaf drop. You may notice your plant loses most or all of its leaves as days shorten and cool. This is normal for this species during dormancy, as they lose their foliage to conserve energy. They suck nutrients out of them and pull them into their roots for safekeeping.

If you notice mushy or rotten leaves, there may be an issue with your plant’s roots. Excessive water and warm temperatures during dormancy may lead to root rot, as they confuse the petunia while it tries to rest. Water when the soil dries, and keep your dormant plant in a cool location to keep it thriving indoors.

Step 8: Harden Off Potted Plants

A close-up shot of pink flowers in pots near a window, taking in the bright sunlight. — It usually takes two weeks to harden off these flowers.

As days lengthen and warmer temperatures arrive in spring, you’ll want to bring your potted calibrachoas and petunias outdoors to let them bask in the sun. An important first step before you bring them fully outdoors is hardening them off.

Harden them off with two weeks of gradual exposure to outside elements. After growing indoors for months they need some coaxing them to come out of dormancy. Bring them outdoors during the day after the danger of spring frost has passed. Place them in partial shade or dappled sunlight, and water them as their soil dries. They may need more water now than during winter, so watch them closely to ensure they don’t fully dry out.

If frost is forecast at night, bring the containers indoors until the next day. After two weeks of hardening off, they should be ready to move to their final location. You’ll notice new leaves, buds, and sprouts growing off of the previously bare stems.

Step 9: Move Pots To Final Location

A person wearing jeans, a grey long sleeve shirt and a bright patterned garden gloves, transplanting pink flower seedlings, in a garden flower bed during the spring. — Place the flowers in full sun or partial shade.

After hardening off, your containerized petunias and calibrachoas are ready to move into their final spot! Place them in full sun or partial shade, where they’ll receive regular airflow. If you grew them last year in a location they like, use it again for guaranteed success.

When your plants awaken in spring with new growth, they’re hungry for nutrients! Apply compost or organic mulch on top of the soil, and add a regular dose of balanced organic fertilizer once your plants start growing leaves and new shoots.

Petunias, although perennial, often live short lives of two to three years. You can overwinter them as long as they live using these nine steps. If you notice your plants starting to die, use this simple guide to take cuttings and propagate new ones.