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Best expert advice on growing petunias

Petunia ‘Amore Queen of Hearts’ from Suttons

For the best advice on growing petunias, we turn to the green-fingered bloggers, YouTubers, and Instagrammers who, between them, have many years experience of growing these popular flowers. Whether you sow petunia seeds or prefer to buy trays of petunia plug plants, here are some excellent tips to help you create wonderful, long lasting summer displays in your borders, containers and hanging baskets. 

Contents:

Best advice on sowing petunia seeds

Petunia Seeds ‘F1 Reflections Mix’ from Suttons
An enchanting floribunda in a blend of colours, ‘Reflections Mix’ grows to 30cm tall
Image: Petunia Seeds ‘F1 Reflections Mix’ from Suttons

Fill a seed tray with multipurpose compost, leaving about a centimetre or so free at the top, says Paul Machen at @happysowinghappygrowing. Then, to sow your petunia seeds, firm the surface slightly, sprinkle the tiny seeds over the surface, and water. Part one of Paul’s seed sowing video is an excellent demonstration of exactly what you need to do.

Stick with Paul over at @happysowinghappygrowing, for part two of his video guide which sees him pricking out his petunia seedlings and transplanting them into a cell tray before putting them into a heated propagator. “Never hold them by the stem, when you’re transplanting them,” Paul says. “Always hold them by a leaf.” 

Once you’ve pinched out your petunias, and potted them into a quality multipurpose compost, you can expect to see their growth rate accelerate dramatically. Soph at @sophsgardendiary says, “I pinched out the million bells (small petunias) about a week ago and wow! I can’t believe the difference.” Head over to her Insta for some very impressive ‘before and after’ pics.

If you’re tempted to save the seeds from last year’s petunias, Sarah at @seahart87 explains why this isn’t always a great idea. As her photos show, second generation petunias can change shape and have a disappointing colour. “Whilst they did have a high germination rate, the flowers themselves haven’t been great,” she says. When it comes to petunias, it’s best to buy fresh petunia seeds.

Best advice on planting petunias

Petunia Frills & Spills™ ‘Damson Ripple’ from Suttons
‘Damson Ripple’ features a beautiful two-tone flower and a heavenly scent
Image: Petunia Frills & Spills™ ‘Damson Ripple’ from Suttons

If you’re wondering how many petunias to plant in your hanging baskets, you’ll find Richard’s advice over at GrowerExperts.com extremely useful. Not only does he run you through all the main petunia types, he also explains how to set up your hanging baskets to display these wonderful blooms to their full potential. Top tip: Richard recommends one petunia plug plant for every inch of circumference. 

For another great way to plant up your petunias, just take a look at Sophie’s gorgeous pallet petunia planter over at @lookinsidemygarden. We dug out her really cool how-to video from last year that demonstrates how she put it together. Even better, she shared her thoughts on how to improve the display planter with the benefit of hindsight! Great stuff Sophie. 

The best advice for gardeners wishing to plant trailing petunias in their hanging baskets is to get your growing medium right. Over at DIY Gardening, Daniel Woodley and Hannah Miller recommend a mixture of multi-purpose compost, coconut coir and perlite. “The compost adds nutrients; the coconut coir holds moisture but drains excess water and improves aeration, and the perlite creates small voids and also absorbs moisture which the roots can extract later in the day as the mixture dries.”

Best advice on caring for petunias

Petunia Plants ‘Surfinia Purple’ from Suttons
Rapid growing and weather resistant, surfinias brighten up gardens all summer long
Image: Petunia Plants ‘Surfinia Purple’ from Suttons

Including petunias in your hanging baskets makes for a spectacular display, as you’ll see when you head over to Soph’s Insta, @sophsgardendiary. But be warned – beautiful hanging baskets require regular maintenance and a keen eye: “Deadheading and watering must be done every day, I always do mine about 8/9pm so they have time to soak the water up overnight,” explains Soph. 

There are two rules to deadheading petunias, says Ray at YouTube channel, Grow Your Own: “Clip off the blooms once they turn brown, and cut off the stems directly above the next set of leaves.” If you just pluck off the dead flower, you leave the seed pod in place, Ray explains. If you want to see exactly how it’s done, we highly recommend that you watch Ray’s clear and informative video guide.

If you notice powdery mildew on your petunias’ leaves, you should treat it straight away, says Paul Machen over at @happysowinghappygrowing. Otherwise it stunts their growth and leads to very disfigured plants. All you need to do is place the plants somewhere out of direct sunlight and give them a good spray with an anti-fungal solution.

Can you see a distinct yellowing between the veins of your petunia leaves? This is a condition known as interveinal chlorosis, explains the team at DIY Gardening. The cause is a lack of either iron or magnesium in the soil. Not sure which problem to treat? “Iron deficiency causes interveinal chlorosis in new leaves and growth, while magnesium deficiency causes it in older leaves,” say Daniel and Hannah. Check out their excellent article to find out what you should do.

Although petunias are often grown as annuals, one of the best ways to get another season from your plants is to overwinter petunia cuttings. Over at YouTube channel, Gardening Wise, Mahwish takes you through the process of planting cuttings. Her advice is to remove lower leaves and any flowers until you have a cutting of three to four inches long. Poke the stems into a pot containing good quality potting compost, bring it inside, and put it on a bright windowsill. See her video for more. 

Best petunia varieties to try

Super Petunia (Beautical) Plants in Cinnamon from Suttons
Super petunias have been bred to outperform other varieties
Image: Super Petunia (Beautical) Plants in Cinnamon from Suttons

How about giving the new super petunias from Suttons a try? This article explains that super petunias (Petchoa ‘Beautical’) are an exciting new hybrid of petunia and calibrachoa. This hybrid flowers for longer, the blooms are rain-resistant and they’re non-sticky, making them easier to deadhead. Super petunias are also bred for vigour, making them resistant to mildew, helping the leaves to stay fresh and green all summer long.

I didn’t think there could possibly be anything more wonderful than a Night Sky Petunia until I saw a bee on a Night Sky Petunia,” says Becky Searle from @sow_much_more! She says, “if you haven’t grown these before they’re awesome (in my opinion!). Each flower is different, and so varied.” Head over to Becky’s Insta to see what she’s talking about.

We hope you’ve enjoyed our collection of some of the best online content on growing petunias. Now all you need to do is to choose from the many lovely varieties on offer here at Suttons. Don’t forget, if you’re looking for advice on growing your favourite fruit and vegetables, our ‘growing guides’ offer a wealth of gardening knowhow. 

Lead image: Petunia ‘Amore Queen of Hearts’ from Suttons

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