Overwintering Petunias: Growing Petunia Indoors Over Winter

Overwintering Petunias: Growing Petunia Indoors Over Winter

By: Jackie Carroll

Gardeners with a bed full of inexpensive bedding petunias may not find it worthwhile to overwinter petunias, but if you are growing one of the fancy hybrids, they can cost more than $4 for a small pot. This means that you might not be able to use them as freely as you’d like. You can save money by bringing your petunia indoors over winter.

Care of Petunias During Winter

Cut the petunias back to about 2 inches (5 cm.) above the soil and plant them in pots before the first fall frost. Check them over carefully to make sure they aren’t infested with insects. If you find insects, treat the plants before bringing them indoors.

Water the plants thoroughly and place them in a cool but above freezing location. Look for a spot in your garage or basement where they’ll be out of the way. Check overwintering petunias every three to four weeks. If the soil has dried out, give them just enough water to moisten the soil. Otherwise, leave them undisturbed until spring when you can transplant them back outdoors.

Can You Overwinter a Petunia Plant as Cuttings?

Taking 2 to 3 inch (5-7.5 cm.) cuttings before the first fall frost is a great way to overwinter them. They root readily, even in a glass of plain water; however, the roots become a tangled mess if you put more than one cutting in a glass. If you are rooting several plants, you’ll probably want to start them in small pots.

The cuttings root so easily that you won’t have to cover them or start them in a greenhouse. Just remove the lower leaves from the cutting and insert them 1.5 to two inches (4-5 cm.) into the soil. Keep the soil moist and they will have roots in two or three weeks.

You’ll know the cuttings have rooted when a gentle tug doesn’t dislodge them. As soon as they root, move them to a sunny window. They won’t need fertilizer over winter if you’ve planted them in a good commercial potting soil. Otherwise, feed them occasionally with liquid houseplant fertilizer and water them often enough to keep the soil lightly moist.

Caution About Patented Plants

Check the plant tag to make sure it isn’t a patented plant before taking cuttings. Propagating patented plants by vegetative methods (such as cuttings and divisions) is illegal. It’s fine to store the plant over winter or harvest and grow seeds; however, the seeds from fancy petunias don’t resemble the parent plants. You’ll get a petunia if you plant the seeds, but it will probably be a plain variety.

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Can you keep petunias over winter?

Care of Petunias During Winter Water the plants thoroughly and place them in a cool but above freezing location. Look for a spot in your garage or basement where they'll be out of the way. Check overwintering petunias every three to four weeks. If the soil has dried out, give them just enough water to moisten the soil.

Also Know, can you keep petunias indoors? Petunias are relatively easy to grow and maintain, blooming from spring until first frost in mild climates. Although petunias are usually grown outdoors in window boxes, containers or flower beds, they can also thrive indoors if you put them near a sunny window and give them regular care.

Hereof, how do you keep annuals alive in the winter?

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.

What is the lowest temperature petunias can tolerate?

(16 to 18 C.). However, petunias usually tolerate temperatures as low as 39 F. (4 C.) with no problem, but they are definitely not plants that will survive the winter in most climates.


Can I Keep It?

This article goes over techniques for overwintering plants that must remain green and growing through the winter.

This article goes over techniques for overwintering plants that must remain green and growing through the winter.

As summer fades into fall, a gardener's thoughts turn to saving favorite plants for next year. With hardy perennials and shrubs the plants can be left to fend for themselves with little more than fall clean up and in some cases a nice mulching. Annuals are going to have their last hurrah and will eventually succumb to the freezing temperatures of fall nights. This leaves us with tropicals, tender perennials and a few assorted plants that can be overwintered in the house.

Many of us have favorite plants that we would like to overwinter and keep for next spring. Which plants are good candidates to bring inside for the winter? Many tropicals and plants sold as houseplants will do fine through the winter indoors. Foliage plants tend to be better suited to overwintering idoors than full sun, flowering plants because they adapt more quickly to indoor conditions.

Tropical – very tolerant of indoor conditions

Tender Perennials – usually need a sunny window

Full Sun Annuals and Perennials

VERY Difficult

banana, philodendron, dieffenbachia etc…

flowering maple, impatiens, begonias, Streptocarpella, sweet potato vine, coleus, geranium etc..

petunias, zinnia, phlox, calibrachoa etc…

There is nothing wrong with trying to bring any plant through the winter indoors. Your likelihood of success is higher with the plants I've listed as easy or very easy, but the worst that will happen is the plant won't make it. You can chalk those attempts up as learning experiences. Gardening is all about trying new plants or old plants in new places. Sometimes it works, sometimes it doesn't. Half the fun is in trying!

What is it about the inside of a house that makes it difficult for many plants? You probably would guess that low light levels are one potential problem. Your home has lower light levels to begin with and the short days of fall and winter also contribute to the problem. The second reason many plants don't adapt to indoor conditions is low humidity. The air inside your home, especially in winter, tends to be very dry. Many plants do not deal well with low levels of humidity. These two factors combined mean that many plants are not cut out to live indoors. Let's say that despite the many challenges you would like to try and overwinter a plant in your home.

The first thing to do is choose the plant or plants you want to bring inside. Be sure to bring your plants inside before frost has damaged the foliage. Choose only healthy plants to bring inside as the stress of the move will likely be the final blow to struggling plants. Of the plant is already in a pot you can skip to the next paragraph. If the plant is in the ground, use a sharp spade or shovel to dig up the plant. You will want to try and get a good chunk of the root system. Remove part of the garden soil and place the plant in a pot. Fill in with a good potting mix. Garden soil tends not to have enough air space for container plants. Keep the soil level even or very slightly above the level of the garden soil. If you bury a plant too deep it will not be happy.

If the plant has been in a rather sunny area you can help decrease the shock it will experience coming indoors by placing it in a shady spot for a week or so. This will get it used to lower light levels and make the transition easier.

Next decide if the plant needs to be pruned before you bring it inside. Plants can generally be pruned back by as much as 1/2 without damaging the health of the plant. When pruning use a sharp pair of pruning shears or scissors, you can also use a sharp knife. Clean your utensils between each plant. Use soapy water, rub them with alcohol, or dip them in milk (odd as it may seem milk will help prevent many viruses from spreading.) Be sure to remove any damaged or diseased portions of the plant.

Once you have your plants potted and pruned it is time to inspect them for debris, disease, and insects. Remove any dead foliage or other debris from the top of the pot. Dead and decaying foliage is a hiding place for insects and an incubator for diseases. Clean plants tend to be healthier.

Check for any insects and treat as necessary. It is important to remove insects before plants come inside. Insect populations tend to increase and spread quickly indoors. In the case of larger insects, like beetles, you can remove them by hand. If you see aphids or spider mites you will want to use a spray to kill them. If the infestation isn't large you can probably remove them by spraying the plant with a mixture of soap and water. A few drops of dish soap in lukewarm water can be very effective means of controlling insects. Spray the plant until it is dripping with the soapy mixture, be sure to get the underside of the leaves and the stems. If you can visibly see insects (like aphids and spider mites), you may want to take a damp cloth and gently wipe off the infested leaves and stems. For obvious reasons it will be easiest to use this method outside. There are also products that you can buy to treat for insects. Safer's soap is a common one. If the plant is badly infected with aphids, mites or scale you should consider discarding the plant rather than trying to bring it indoors.

While checking for insects also look for disease. Common diseases include mildews and viruses. Mildew will generally be a white or grey powdery substance. Viruses will often cause the plant to have foliage that is yellowing, mottled, or stippled, the foliage just doesn't look right. Mildew can be treated with the same soap and water mixture used against insects. If you think your plant has a virus discard it and start new next spring.

Water the plant thoroughly before bringing it inside. Be sure to allow a good amount of water to run out of the drainage hole. This will help flush out any excess buildup of salt or fertilizer in the soil. You may want to follow this flush with a light fertilizer application.

Move your plants indoors and place them in areas with bright light. If you have a sun porch you are lucky and should be able to overwinter many plants fairly easily. You can use grow lights for supplemental light if you feel the interior of your house is too dim.

To help combat low humidity place a shallow pan filled with gravel (it is best to buy gravel from the store where it will be clean, if you get gravel from your driveway be sure to wash it well) underneath your plants. Add water to the gravel. This water will evaporate keeping the area right around your plants more humid. You can also spray the area with a spray bottle a couple of times a week to help increase humidity.

While the plants are inside do not fertilize (unless the plant is growing vigorously then fertilize lightly once a month or so). You will also need to be careful not to over water. Plants inside will not use as much water as they did outside. Water only when the top of the soil is dry to the touch. When you do water try and dampen the whole root zone (a bit of water should drain out of the bottom of the pot.) It is very easy to accidentally kill your plant with kindness.

Plants in lower light situations will have a tendency to stretch and become lighter green in appearance. Don't worry too much about this problem. If you can keep your plant alive till spring you can deal with the stretched plant later.

In spring when the days start to get longer you should see your plant begin to grow more vigorously (or again, some plants may not grow through the winter). When this new growth starts fertilize lightly with a water soluble fertilizer. Prune your plant back if it is looking stretched and unhappy. Your plant is likely to begin using more water at this time so be sure to keep an eye on how quickly it is drying out. Lightly pinching new growth will encourage your plant to branch.

Once you start getting warm days, you may want to start introducing your plant to outdoor conditions. Moving plants outside during the day and inside at night will help harden it off. Plants are like people that first 40 degree day seems awfully cold. However, after a week of 20 degrees, 40 feels downright nice. Gradually introducing a plant to cooler temperatures (hardening off) will help it acclimate to outdoor conditions. Once the threat of frost has passed, place the plant outside permanently.

This article should help you successfully overwinter your favorite plants.

Rules of Thumb for Overwintering Plants Indoors:

1. Choose only healthy plants

2. Bring Plants indoors before frost damages foliage

3. Treat for disease and insects before bringing plants indoors

4. Place in bright areas and add humidity using pebble trays or spray bottles

5. Be careful not to over water

6 When active growth starts in spring fertilize and prune as needed

7. Introduce your plants slowly to outdoor conditions in spring


Overwintering Calibrachoa Indoors

Overwintering potted calibrachoa plants outdoors is especially difficult, so bringing them indoors is the best option. Move them to a bright, moderately warm room with at least six hours of good sunlight each day, such as near a south- or west-facing window. A room where temperatures stay above 60 degrees Fahrenheit is ideal just position the pot away from any heat sources such as heater vents or fireplaces because the plants may develop thin, spindly growth when exposed to too much heat, according to the University of Vermont Department of Plant and Soil Sciences.

Both too little and too much moisture has a detrimental impact on calibrachoa as it overwinters indoors. Water whenever the soil feels dry just beneath the surface, adding water until a little bit trickles from the base of the pot. Humidity can be an issue indoors, particularly in the winter, so try placing the pot on a tray of wet pebbles to increase humidity around the foliage. Move the calibrachoa plants back outdoors in spring after nighttime temperatures warm to above 55 degrees Fahrenheit.


Mexican petunias are a favorite plant in the desert, but they also grow well in humid climates. They do not survive in the cold, yet they can still be enjoyed as summer annuals in areas that experience low temperatures in the winter.

While it's not mandatory, Mexican petunias benefit from the addition of manure, fertilizer, and compost in their growing areas. In the springtime, you can use a garden rake to mix in a fertilizer of choice into the top 2 inches of the soil surrounding the plants.

If you're planting Mexican petunias for the first time, you may want to use a shovel or garden tiller to loosen and turn over the soil before planting, sprinkling in compost or manure as you work. To improve drainage in moist beds, consider adding a little sand to the mix.


Cuttings or Potted Plants?

If you are blessed with a greenhouse or have ample window space, the easiest way to overwinter your annuals is to bring them indoors before they are killed by frost. If, like me, you only have a few windows you can take cuttings of these plants (except for Oxalis) and root them on your windowsills. You don’t need any fancy equipment. An empty canning jar like the one in the post on taking tomato cuttings works fine.

Sometimes bugs can hitch a ride indoors through potted plants. Rinse off the foliage (paying close attention to the underside of leaves) with the garden hose before bringing them indoors. Bugs aren’t really a problem with cuttings, but give them a blast from the hose just in case.


Planting and Care

In Florida, October and November are the best time to plant petunias. Petunias will grow best in full sun and well-drained soil that is kept moist. If you're planting petunias as a groundcover, be sure to space plants 12 to 18 inches apart. Petunias should be given at least 1 to 2 inches of water every 7 to 10 days once established. Light, frequent waterings should be avoided as it will encourage shallow rooting. Fertilize your petunias monthly with a balanced fertilizer or use a controlled-release product such as Osmocote or Dynamite at the time of planting.

You can pinch off the top inch of petunia plants to encourage good branching. Deadheading is necessary on large-flowered and double petunias while many of the smaller flowered cultivars are self-cleaning. Gardeners in North Florida may have to protect their petunias from frost.

Petunias have few serious insect or disease pests. Aphids and caterpillars may be an occasional problem. Petal blight can be a problem in rainy and very humid weather avoid getting leaves or flowers wet when watering. Viruses occasionally affect petunias. Modern petunias have been hybridized with disease-resistant old fashioned types to resist botrytis rot. These hybrids are also more tolerant of temperature extremes and produce more flowers. The 'Wave' hybrids were created to tolerate warmer temperatures.

With just a little bit of work petunias can provide you with cool season color and cheer in your landscape. For more information on growing petunias in your area contact your local county Extension office.


Watch the video: Are Petunias Annual or Perennial?