By Sarah Wilson
Find out how to grow petunias and you’ll be adding spectacular color to your planting that will last for months on end. There’s a petunia for every type of garden set-up from balconies and roof gardens to cottage style borders and modern urban spaces.
They’re available in every color combination you could possibly want too. What's more, these prolific plants keep flowering right through summer into autumn. Petunias make excellent patio, bedding and border plants, producing wonderfully bright flowers right into autumn.
Choose from trumpet shaped or double ruffled blooms, or more subtle ones featuring delicate marbling detail on their petals. They look particularly spectacular planted in a solid color block of magenta pink, inky purple or dark crimson.
With new varieties coming on the market all the time it’s worth keeping a look out for something a bit different this year. The more unusual varieties include soft lime green if you like neutrals or velvety black ones for that monochrome look. Check out the Tidal Wave varieties too as they hardly need any deadheading.
Read on to find out more about our recommendations on how to grow petunias and don’t miss our flowerbed ideas for more planting inspiration.
How to grow petunias
Follow these key pointers on how to grow petunias and help your plants to thrive.
- Petunias are happiest in full sun but will also do well in shady spots.
- They grow best in a sheltered position.
- Petunias can cope with any type of soil but it must be moist and well-drained.
- They establish themselves easily and are straightforward to grow.
- Feed regularly throughout summer to encourage more flowers.
- You need to deadhead them regularly to prolong the flowering season.
- They flower prolifically from June through to October.
- They look spectacular in containers, window boxes, hanging baskets and borders.
- Petunias suffer from very few serious insect or disease pests. Avoid wetting the foliage and flowers when watering though to help prevent disease.
- There is a huge range of different colors, sizes and varieties to choose from.
What month is best to plant petunias?
Petunias can be generally be planted outside from early May, but you need to make sure there's no danger of frost.
Garden centers are packed with young plug plants but these are tender and cannot be planted out until risk of frosts is over, usually mid to late May if you live in a climate similar to the UK.
How to plant petunias
Look for plants that are short and compact, not leggy and not yet flowering as they’ll settle into their new spot faster.
For container gardening ideas, try planting three or four plugs in a large pot for a full display come June. Use fresh potting compost when planting and make a hole deep enough to accommodate the young plant comfortably.
To start with, water every three to five days, take care not to get the foliage wet when watering as this can damage the plant and promote disease. It's best to water carefully from the base of the plant, close to the soil. Check the wetness of the soil beforehand to make sure you're not overwatering them.
What varieties of petunia are there?
There are lots of different types of petunia to choose from, so there's guaranteed to be one for every occasion when you're finding out how to grow petunias!
- Multiflora varieties are bushy and grow up to 15cm tall.
- Grandiflora are bigger and tend to have double or frilled flowers but less of them.
- Pendula varieties have long stems suitable for trailing over the edges of baskets so are a great choice for window box ideas.
Which petunias are best for window boxes and hanging baskets?
Surfinia petunias were the first trailing petunias to be developed and have become a must-have for window boxes and hanging baskets ideas, especially as they flower abundantly all summer long. They’re available in a stunning range of colors too.
What’s a good petunia for patio pots?
By combining petunias and calibrochoas breeders have created petchoas, a good choice for your patio gardening ideas. They’re easy to grow, sun-loving annuals that come in a fabulous range of colours and create an attractive billowing form.
Million bell petunias are another star of the patio plant scene, smothered in a mass of small, prolific flowers. Available in a range of colors, they flower practically non-stop and don’t need deadheading. Technically these plants are not petunias but calibrochoas. This means they’re a little more drought tolerant making them a good choice for containers.
Can I grow petunias from seed?
Thinking about trying how to grow petunias from seed? If you want to give this a go, start them indoors about 10 weeks before you want to plant them outside. Petunia seeds are very fine and dust-like so you need to be careful when handling them. They also needs lots of light and plenty of water in order to germinate. When the plants have three leaves, it's time to transfer them out to the garden.
It's always pleasing to learn how to grow flowers from seed, but with so many affordable plug plants to choose from at the garden center it might be easiest to opt for those.
How do you take care of potted petunias?
One of the key things to know about how to grow petunias is that petunias love their food! Apply a slow release fertilizer when you plant them, then follow up with repeat liquid feeding every couple of weeks throughout summer. Make sure they get plenty of full sun too – at least six hours a day if possible if you want to be sure of getting the most spectacular blooms.
Do petunias grow back every year?
When it comes to how to grow petunias, it’s easiest to treat petunias like annuals and replace them every year. They can end of looking pretty straggly by the end of summer anyway. However, if your plants are still healthy you can try overwintering them indoors in a warm spot from autumn onwards or propagating new plants from your existing stock.
How do you keep petunias blooming?
There are three basic demands for how to grow petunias successfully: sunlight, water and liquid feed. The more sunshine they're exposed to the more flowers they will produce. When it comes to watering plants, check the soil daily with your fingertip and make sure it stays hydrated. But if your foliage begins to turn yellow, it’s a sure sign that the roots are probably waterlogged so it's time to cut back on the watering routine.
More than anything else, fertilizing every seven to ten days is a must to keep plants well fed and covered with flowers.
How do you stop petunias going straggly?
By midsummer, petunias can start to get a little leggy, producing blossoms at the tips of long, leafless stems. To keep them tidy and producing more flowers, prune the shoots back to about half their length. This will encourage more flowers. After pruning, fertilize and water the plants well to encourage new growth and more flowers. The plants may look ragged at first but they’ll soon bounce back better than ever.
Another necessary task when learning how to grow petunias is to remove faded, old or dead flowers to get more blooms and improve the look of your plants, especially for the larger-flowered petunias. Dead-heading prevents seed pods forming which will compete for the plant’s food supplies. Clippings can be added to a compost pile to be recycled. You can find out how to compost in our guide.
WHERE TO BUY PETUNIAS
Ready to follow our tips on how to grow petunias and add them to your outdoor space? You can buy young plug plants from the garden center or online to get you started. Shop petunias at the below suppliers, or keep scrolling for some of our favorite picks.
Where to buy petunias in the UK
- Shop petunias at Amazon
- Shop petunias at Crocus
- Shop petunias at Dobies
- Shop petunias at Suttons
- Shop petunias at Thompson & Morgan
- Shop petunias at Waitrose Garden
- Shop petunias at You Garden
Where to buy petunias in the US
- Shop petunias at Amazon
- Shop petunias at Burpee
- Shop petunias at Home Depot
- Shop petunias at Target
- Shop petunias at Walmart
4 varieties of petunia to try in your garden
With so many wonderful colors and varieties to choose from you're spoiled for choice. Here's a round-up of some of our favorite varieties of petunia.
Petunia 'Potunia Dark Red' from Crocus
Forms a natural dome crowned with a profusion of rich red flowers from early summer. Grown in individual 13cm pots, these plants are ready to be planted out once all risk of frost has passed. Likes a spot in full sun and moderately fertile, well-drained soil. Flowers from May right through to the first frosts.
Petunia Surfinia Trailing 'Hot Pink' from Thompson & Morgan
Recently awarded a prestigious RHS Award of Garden Merit, Petunia Trailing Surfinia 'Hot Pink' is world renowned for its flower power, weather resistance, color range and versatility. With long trailing stems it's ideal for creating a cascade of color from hanging baskets and window boxes. Trails to: 90cm.
Petchoa hybrida 'BeautiCal French Vanilla' from Sarah Raven
This petunia has a kind of grandeur about it and is as chic as you can get. And it's super-abundant and easy to grow too. It will thrive in a container but will require protection until after the last frosts. Gradually acclimatize plants to outdoor conditions for 7-10 days before moving to their final position.
Petunia 'Night Sky' from Suttons
Petunia 'Night Sky' had already won a Fleurostar award by industry insiders and has now received a prestigious RHS Award of Garden Merit. The launch of this special flower marks a breeding breakthrough, as no other petunia plant has the starry speckled pattern of this unique bloom. Perfect for baskets and patio tubs!
Love the idea of adding some of these varieties of petunias to your hanging baskets this summer? Head over to our guide on how to make a hanging basket for top tips on creating a stunning design.
Sarah Wilson has been a lifestyle journalist for many years, writing about gardens since 2015. She's written for Gardeningetc.com, Livingetc, Homes & Gardens, as well as Country Homes & Interiors and Modern Gardens magazines.
Her own (small urban) garden is a work in progress - so many ideas, not enough space to cram them in. Hero plants include her ever growing collection of ornamental grasses, black bamboo and ferns, and the perennials like salvias and penstemons that come back reliably year after year. All very restrained though when in fact she'd love to pack her garden with gaudy dahlias and giant cannas, so these are top of her wish list for what to grow next.
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