Many gardeners heap scorn on petunias, but I’ve always had a soft spot for these summer annuals which are available in a myriad of colours and forms including the perennial varieties sold as Million Bells or calibrochoa.
Petunias flower in red, purple, pink, yellow or white or the flowers may display combinations of these colours. They can be large or small flowered and some have doubled or ruffled blooms.
They can look gaudy, especially when grown as a mass of different colours but they are a fast and fool proof way to inject colour into your garden for summer. To minimise the riot of colour, choose colour mixes seedling varieties, or limit your planting to one or two colours that match the colour scheme in your garden. Boldly coloured petunias can also be used to add highlights to a green garden or enliven an outdoor entertaining area such as a barbecue area or around a swimming pool.
Apart from their brilliant colour, I also like petunias because they are tolerant of both heat and humidity. Even if they are hit by a hot dry gusty day, or a heavy storm, most bounce back without too much damage.
The best heatproof petunias are those with smaller flowers as these generally cope with both the high temperatures and the wet of summer.
Planting and growing tips
Petunias can be grown in the garden or in containers including hanging baskets. They need a sunny spot and grow best with regular watering and the addition of a liquid plant food every two to three weeks. Petunias need at least six hours of sun but full sun from morning to mid afternoon brings on the best performance from these plants.
You can buy petunias as seed, seedlings, small flowering pot plants (bloomers) or as flowering hanging baskets. Seed is planted from late winter to summer and seedlings are available from late winter. Petunias are frost sensitive so avoid planting petunias out in the garden until all threat of frost has past.
Expect plants to take around 12 weeks from seed sowing to flowering. Petunia seedlings may bloom in six to 10 weeks from planting into a pot, hanging basket or garden bed.
Give seedlings or small plants a good soaking in one of the seaweed solutions before planting to avoid transplant shock. Soaking also ensures the root balls are moist all the way through before they are planted out into the ground or a pot.
As the plants grow, ‘tip prune’ them to encourage branching growth. Tip pruning just means pinching out the soft tip growth using your fingers or secateurs to encourage the pair of shoots below the tip to branch out.
When flowering begins, regularly remove spent flowers to keep plants compact and producing more blooms. Petunias tend to die back towards the end of summer or into autumn. At this stage most plants can be removed to make room for autumn and winter plantings. Perennial forms can be cut back at this time and may regrow and re-flower in spring.
Protect seedlings from snails and slugs (use snail baits or regular inspections). Also check plants for caterpillars such as loopers or cabbage white butterfly larvae, which may feed on the flowers or leaves. Squash any you see or apply a garden spray to kill caterpillars such as Dipel or Yates Success. Always apply chemicals according to the label instructions.