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Purple petunia flowers in a hanging basket
A popular annual flower and perennial hybrid, petunias are easy to grow, and bloom prolifically. Annual plants are sold as seedlings and potted colour. Short-lived perennial forms called petunias are actually calibrachoa (sometimes known as “Million Bells”), a plant closely related to petunias.


What you need to know about petunias

Name: petunia, calibrachoa.

Height: 20–100cm wide by 10–40cm tall.

Foliage: green and downy with rounded tips. 

Climate: all areas. 

Soil: well-drained, improved with compost. 

Position: full sun or part shade (need at least 6 hours of sun). 

Flowering: year-round in warm climates. 

Feeding: feed fortnightly with a liquid fertiliser. 

Watering: daily in pots and while establishing. Water when soil dries out.

Appearance and characteristics of petunias

Petunias are low spreading or mounding plants with wide, trumpet-shaped flowers and branching foliage that is downy and sticky. 

The plants are related to tobacco, and have flowers that are 3–4cm wide. They can be single, double or ruffled, and the petals striped, veined, spotted, bi-coloured or solid colours. The growth habit can be either mounding or cascading. 

Petunias are available in every colour except true blue and orange, and are a fast way to inject some colour into the summer garden. 

Calibrachoa have a compact or trailing habit and flower continuously, with smaller flowers and foliage than petunias. Most flowers are about 1cm wide, and their colour range includes orange and bicolours. Many forms also feature a coloured throat. 

Petunias are grown during the warmer months in cool climates and year-round in warm areas of Australia. They are tolerant of heat and humidity, but are not frost tolerant, so wait until all threat of frost has passed before planting. 

They need at least six hours of full sun each day, but in the heat of mid-summer it’s best to move pots into partial shade. Extreme heat may cause them to stop setting flowers, but they will bloom again when the temperature drops. 

Petunias bloom prolifically and keep flowering for many months if the spent blooms are deadheaded. They are prone to disease in continually wet weather. 

Spreading petunias make great ground covers, and trail down the sides of hanging baskets and pots. 

Annual petunias can be grown from seed sown in late winter, but it will take about 10–12 weeks from sowing the seed until the seedlings are ready to plant out. 

Most people buy seedlings, in punnets of eight, ready to plant out. Advanced seedlings are a little more expensive, but flower almost immediately after planting. Plants are also sold as potted colour that is already flowering. 

A purple and white petunia flower in a garden

Varieties of petunias 

The most popular and widely sold forms of calibrachoa are the “Million Bells” series, bred by the Japanese company Suntory. Other varieties are the Colourburst and Selecta series. New varieties of petunias are released most years and are available in punnets as mixes of colours or single colour ranges. 

Uses for petunias

Petunias are an inexpensive way to add flower colour to pots, hanging baskets and garden beds. With the wide range of colours and forms available, there is a flowering petunia to suit all colour schemes. 

How to plant and grow petunias

  1. Soak the seedlings in a weak seaweed solution to reduce transplant shock and encourage root growth.
  2. Plant into the garden, pot or hanging basket.
  3. Water the plants in well once they have been planted into their final position.

Caring for your petunias

Petunias are perfect pot specimens, and should be planted into free-draining soil that’s been improved with compost. While it is best to provide fertiliser into the soil when the petunias are planted, fortnightly to monthly foliar feeding with a liquid fertiliser will provide the nutrients for petunias to remain constantly in bloom.

How and when to prune petunias

  • When planting, pinch the seedling back to encourage more branching and a fuller plant. Tip pruning means to pinch out the soft tip growth using your fingers or a pair of scissors or secateurs. This encourages the pair of shoots below the tip to send out two shoots. You may wish to cut them back harder during mid-season to make straggly plants bushier. 
  • After a few months, annual petunias will flower less and start to die back. Remove the plants, improve the soil or refresh potting mix in containers. To maintain colour in late autumn and winter, plant some annual seedling plants like pansy and cineraria.
  • Calibrachoa should be trimmed back in cooler areas when it stops flowering. It will bloom again when the weather warms in spring.

Diseases and pests affecting petunias

Protect seedlings from slugs and snails by using snail baits or beer traps. Hose aphids off with a strong blast of water or use a pyrethrum spray, and check plants for caterpillars, which eat the flowers and leaves. Squash them or apply a caterpillar spray like Dipel or Yates Success.

If you like this then try

Marigolds: small, vibrant yellow or orange-coloured annual plants that flower prolifically through the warmer months in pots and garden beds. 

Annual salvias: small annual to short-lived perennial plants. Available with white, blue or red flower spikes, they are perfect for pots and bedding plants, flowering prolifically in the warmer months.

Pansies: rich and brightly coloured flowers with dark blotches, flowering from late winter through to spring. 

Start planting today

Check out our huge range of plants now and get your garden growing.


Health & Safety

Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.

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