Caring For Petunias: How To Grow Petunias

Caring For Petunias: How To Grow Petunias

By: Becca Badgett, Co-author of How to Grow an EMERGENCY Garden

Growing petunias can offer long term color in the summer landscape and brighten dreary borders with lovely pastel colors. After learning how to plant petunias you can include them in your flower bed and container garden.

Four species of petunias include hundreds of cultivars and offer a perfect addition to the home landscape:

  • Grandiflora petunias are the most common type of growing petunias. This species features 3 to 4 inch (7.5 to 10 cm.) blooms which often grow upright, but may spill over the side of your container or window box.
  • Multiflora petunias have smaller flowers and a more abundant bloom.
  • Milliflora petunias are miniature versions of growing petunias; they are compact and reblooming.
  • Spreading petunias are only 6 inches (15 cm.) tall and can rapidly cover a selected area to function as a blooming ground cover.

Care of Petunias

Care of petunias includes regular watering and as much sunlight as possible to promote multiple blooms. Spreading ground cover petunias are pickiest about water; weekly waterings should be included in the care of petunias.

While petunias will grow in a partially shaded location, a fuller and more abundant bloom is produced in full sun. Soil prepared before planting petunias should have well-composted organic matter worked in.

Care of petunias will include regular fertilization with a balanced, water soluble fertilizer designed for blooming plants. As they are heavy feeders, petunias care will also include weekly feedings. Proper light, water, and fertilization when caring for petunias will ensure a long season of beautiful blooms.

Proper petunia care involves removing spent blooms and the seeds they may produce. When deadheading the growing petunias, remove the base of the flower to include seed removal. Petunias allowed to go to seed will slow or stop blooming.

Purchasing Petunia Plants

Hundreds of cultivars of petunias are available to the gardener for use in a range of garden designs. Double and single blooms offer a selection of solid and multi-colored flowers.

When purchasing young petunias, choose plants with a compact form and unopened buds. Open blooms on the petunia are best removed after planting for a more abundant show in the future.

Growing petunias is easy and rewarding. As you learn how to grow and plant petunias, you will never be at a loss for a beautiful bloom for a full sun area.

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Petunias are one of our most popular summer bedding plants, flowering throughout summer until the first severe frosts of autumn. Their mass of flowers bring lots of great colour to gardens.

The compact, bushy varieties are perfect for planting in beds and borders and the trailing types brighten up hanging baskets and for flowing down the edges of containers.

There is great variety in petunia flowers: a wide range of colours both single and double blooms smooth or ruffled petals solid single, striped, veined or picotee-edged colours and even fragrance. Recent breeding has also removed the scourge of old petunia varieties – turning to mush in a wet summer.

Petunias are perennial, although most bedding types are grown as annuals from seed each year. The trailing varieties, such as Surfinias, are perennial and are grown from cuttings or new plants.

How to grow petunias


Petunias prefer to be grown in full sun, although during hot, sunny summers they will tolerate light shade. They grow best in a fertile, moist but well-drained soil. Dig in plenty of organic matter – such as garden compost, well-rotted manure or other soil improver – especially in very well-drained sandy soils to hold moisture.

Petunia varieties

Bedding varieties are either grandifloras with larger flowers or multifloras with smaller flowers that hold up better in the rain.

Spreading or trailing petunias include Surfinia, Wave, Tumbelina, Supertunia and Cascadia series.

Sowing petunias

The annual or bedding petunias can be grown from seed sown indoors with warmth in spring in cell trays, seed trays or small pots at a temperature of 18-24°C (65-75°F).

When large enough to handle, prick out plants individually into cell trays or small pots and grow on at a temperature of 50-65°F (10-15°C) in good light.

Gradually acclimatise the plants to outdoor conditions for 7 to 10 days before planting outdoors when all risk of frost has passed.

If you don’t have the facilities to grow them from seed, young petunia seedlings are available from garden centres and mail order suppliers in late winter/early spring.

Planting petunias

Petunias are planted out in May/June after the danger of frost has passed.

Dig a good sized planting hole, big enough to easily accommodate the rootball. Add a layer of organic matter – such as compost or planting compost – to the base of the hole and fork it in.

Place the rootball in the planting hole and adjust the planting depth so that it is planted at the same depth as it was originally growing (except hardy fuchsias) and the top of the roots are level with the soil surface. Mix in more organic matter with the excavated soil and fill in the planting hole. Apply a granular general feed over the soil and water in well. Applying a 5-7.5cm (2-3in) deep mulch of well-rotted garden compost or similar over the soil will help maintain soil moisture and keep down weeds.If you have a warm greenhouse, you can plant up containers and baskets in spring and grow on the plants, ready to place outside in late May/early June. This way you’ll have flowers earlier in the summer.

Suggested planting locations and garden types

Flower borders and beds, patios, containers, city and courtyard gardens, cottage and informal gardens.

How to care for petunias

Keep the soil moist by watering regularly during prolonged dry periods in summer. Plants in containers will need regular, possibly daily watering – the aim being to keep the compost evenly moist. But don’t overwater, as too much water will cause the plants to become leggy with few flowers.

Feed regularly throughout summer with a liquid plant food to ensure a continuous supply of flowers. A high potash liquid plant food will encourage more, better blooms over a long flowering period until the first autumn frosts.

Removing faded flowers and any developing seed pods will prolong the display. Straggly plants can be cut back quite hard and then fed with a liquid plant food to produce fresh new growth and a profusion of flowers.

In the autumn, once damaged by frosts, bedding petunias are best dug up and composted.

Overwintering petunias

Perennial, trailing varieties can be cut back hard in autumn, tidied up to remove dead or damaged growth and carefully lifted. Pot them up in pots just big enough to take the rootball and some fresh potting compost around the sides, and overwinter in a light, frost-free place – preferably a greenhouse or cool conservatory.

Propagating perennial petunias

Perennial, trailing varieties can be propagated from cuttings taken in March/April from overwintered plants or in August/early September.

Choose strong, healthy young stems that aren’t flowering. If you can’t find suitable growth, cut back hard one or two stems at the back of the plants to encourage strong regrowth. Take cuttings 7.5-10cm (3-4in) long, cutting just below a leaf joint, or node. Remove the leaves from the lower two-thirds of the stem and insert five or six cuttings in pots of gritty, cuttings compost to the base of the lowest leaves. Place the pots in a plastic bag or in a propagator and place somewhere in good light, but out of direct sunlight, to root.

The cuttings should have rooted in 2 to 3 weeks, when they can be potted up individually and grown on.

Petunias are one of the most popular plants to grow for people everywhere, and for good reason. They come in a myriad of colors and availability. You can almost always find a color to compliment your décor or other flowers in your landscape.

Petunia are heat tolerant, drought tolerant, and sun tolerant. They love lots of sunlight to get the most blooms.

They work wonderful in containers. They are amazing in hanging baskets and will provide season long blooms of color if taken care of properly.

Let’s face it, petunias in a hanging basket with flowers cascading down over the sides is one of the most glorious sights you’ll see.

Petunias are also some of the fastest growing plants you can buy to beautify your garden. This can result in them becoming leggy and pretty unsightly in a short period of time.

To keep your petunias looking great try to implement these tips during your blooming season. These are techniques I use in the hot, humid southeastern United States. It can seem like a lot of work but by doing a little at a time, you’ll reap huge benefits with these beautiful flowers.

Start With Good Petunia Varieties

The main thing you want to do, as with any plant in my opinion, is to get a variety that suits your needs. It’s very tempting to buy that flat of 12 for 6$ on the bargain shelf.

If you are willing to spend a little more to grow a Wave or Supertunia variety, their performance will blow your mind.

If you are looking to fill a pot for a short time, the cheap ones will do great, but require lots more maintenance.

The aforementioned do not require dead heading or pinching in order to look great for quite a long time.

Water a Little Less Often

How often to water petunias in a hanging basket is probably the MOST common question I hear.

I have had the best luck with my petunias when they are allowed to dry out for a while. Even if you skip a day or two depending on the weather, of course. Sometimes even going past the droopy stage before watering has kicked new life into their blooming habits.

Hanging baskets and containers need to be potted with well draining potting soil or whatever medium you are using so you can give them a deep watering without worrying about their roots sitting in water for any amount of time.

Cut Them Back

Pruning petunias in a hanging basket is the single most important thing you can do to keep them looking their best!

This has to be one of the average gardener’s biggest fear! It took me years to finally break down and start cutting things back. I couldn’t bear to sacrifice blooms for fear of what may happen.

Nowadays I cut almost everything I own back pretty regularly and Petunia’s being the most often. Pinching the ends creates new growth in a very short amount of time.

Cutting the branches back to about 4 inches or so and starting over in early Summer is my newest routine. Once you let them get past a certain point where there are no leaves on the stem, its hard for them to fill in and look nice. If you wait to long, some may never recover.

Feed Them

Petunia’s are heavy bloomers and require lots of sun and energy to make this happen. Fertilizing with a slow release fertilizer is key to keeping them looking good longer.

I recommend a weekly liquid fertilizer as well. You will definitely see a difference once you get into a regular schedule of feeding them.

Treat Them for Pests

You may go an entire season without bug problems. Once the caterpillars find your flowers though, they can wreak havoc on your plants overnight.

Aphids, snails, earwigs and other pesky insects love to chew on the leaves and new tender buds of petunias. Once they hit, they damage is already done and your plant will not look its best unless you cut off the damaged limbs and start over.

It is best to go ahead and treat your plants before it happens.

Pesticides To Use

Bacillus Thuringiensis is the best thing to protect against caterpillars. It comes in a few different commercial products, one being Thuricide.

It is a naturally occurring bacteria that affects the digestive systems of the caterpillar. This is a great product because it won’t harm Bees or other beneficial insects, or your plants!

Insecticidal Soap or Neem Oil is best to treat just about any other pest including Aphids and Mites, without damage to your petunia.

When The Growing Gets Tough

Petunias are a wonderful addition to any garden. They are sold as annuals but in southern Alabama I have one particular Petunia that has come back for the last three years. It all depends on your climate.

They may suffer a bit through the hottest part of the summer, so move them to a part shade area if possible, during this time. Once this time is over though, they will experience a new growth spurt and therefore another wave of blooming through the end of the season.

With a little extra care you can keep your petunias looking great all the way through the season! So get on out there ! I know it’s hot but your Petunias are suffering too !

Try a few of these tips to bring them back to their former glory!

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