Petunias add the perfect pop of colour to any garden, but they are particularly suited to summer gardens for their heat and sun tolerance. Petunias thrive in hot weather and full sun, which would stress out many other flowering plants. They actually perform best when temperatures are warm.

We also love petunias for their low maintenance nature. They’re relatively easy to care for and don’t need much beyond regular watering and occasional fertilising. Many newer varieties are even self-cleaning, so they don’t need deadheading to keep on blooming. A win!

Where to plant petunias for the best results

Plant your petunias in full sun, so that they get at least 6-8 hours of direct sunlight daily. They’ll bloom most prolifically in these conditions. If you plant them in partial shade, they’ll tolerate it but will reward you with fewer flowers.

Ensure that you plant your petunias in well-draining soil. These beauties don’t like to sit in waterlogged conditions, which can lead to root rot. If your soil is heavy clay, consider amending it with compost or planting in raised beds or containers instead. The advantage of adding petunias to your home is that they fit in perfectly in a range of locations. Here are some ideas:

• Front borders or edges of beds where their flowers can spill over
• Hanging baskets near entrances or on patios where you can enjoy them up close
• Window boxes for a classic cottage garden look
• Mixed containers on patios or decks
• As ground cover on slopes or in areas with good drainage

The key is plenty of sun and good drainage – get those two things right and petunias will reward you all summer long.

Learn which plants make great garden companions for petunias.

Watering petunias in hot weather

In hot summer weather, like January and February, petunias typically need watering daily, especially those in containers and hanging baskets. Container petunias may even need watering twice a day during heat waves since pots dry out faster than garden beds. 

Ground-planted petunias usually need watering every 2-3 days, depending on your soil and temperatures.

Water your petunias early in the morning if possible. This gives plants moisture to handle the day’s heat and allows foliage to dry before evening, which helps lower the risk for fungal diseases.

Feeding and fertilising for more blooms

To get a beautiful floral yield from these sunshine showstoppers, use a balanced, water-soluble fertiliser or one formulated for flowering plants. 

Look for something like a 10-10-10 or 20-20-20 ratio, or a bloom-booster formula that’s slightly higher in phosphorus (the middle number), like 15-30-15. The phosphorus promotes flower production.

For container petunias, fertilise every 1-2 weeks throughout the growing season. 

Garden-planted petunias can be fed every 2-3 weeks. 

Since they’re watered frequently (which leaches nutrients from soil), they need regular feeding to keep performing.

Top tip:

You can also use slow-release granular fertiliser mixed into the soil at planting time, then supplement with liquid fertiliser every few weeks. Slow-release feeds plants gradually over several months.

Common petunia problems (and how to fix them)

Petunias not growing the way you hoped? Here are solutions to some common petunia problems:

Leggy, stretched-out growth 

This happens when petunias don’t get enough light or are overfed with nitrogen. 

Solution: 

Move them to a sunnier spot if possible, and give them a trim to encourage bushier growth. Cut stems back by one-third to half, and they’ll branch out and fill in nicely.

Fewer flowers or stopped blooming

Usually caused by inadequate fertiliser, not enough sun, or (for older varieties) spent blooms left on the plant. 

Solution: 

Increase feeding frequency, ensure they’re getting 6+ hours of sun, and deadhead faded flowers regularly if you don’t have a self-cleaning variety.

Yellowing leaves

This often is a sign of a nutrient deficiency, particularly nitrogen or iron. 

Solution:

Increase your fertilising schedule. If only lower leaves are yellow, this is normal as the plant matures. Overwatering can also cause yellowing, so check that drainage is adequate.
Petunias aren’t the only beautiful heat superheroes to add to your summer garden. Here is a list of other heat-resistant plants for inspiration.