When To Plant Petunias In The UK

Once upon a time, all you could buy was a straggly plant with dull-pink flowers which preferred a warmer climate than ours here in the UK.

Petunias are grown as perennials in warmer countries but here in the UK, they are grown as summer annuals.

Like most summer bedding plants petunias on sale around mid to late April depending on the weather. However, it is too early to plant them out in the garden at this time because there is still the risk of a late frost.

Plant your petunias outside with all your other bedding plants when the danger of frost has passed in late May or early June.

Types Of Petunias

There are four main types of petunias available for sale here in the UK, five if you count Million Bells (Calibrachoa) which look like tiny petunias but are an entirely different species.

Grandiflora Petunia

Grandiflora Petunia

One of the oldest varieties that were developed in the 1950s. Grandifloras produce the largest blooms of all the petunia family but bear the least amount of flowers.

This variety does require deadheading if you want them to continue to flower all summer. If spent blooms are left on the stems will carry on growing but no new buds will form.

Grandifloras work well in borders, containers and hanging baskets.

Multiflora Petunia

Multiflora Petunia

Multifloras have a more compact growth habit and smaller blooms than grandifloras but are more prolific in producing flowers.

Wave Petunia (Milliflora)

Wave Petunia

A recent addition to the petunia family, wave petunias can spread up to 4 feet making them a great ground-cover or hanging basket plant.

The variety called ‘Tidal Wave’ can grow to 6 feet in height with a 3-foot spread.

Surfinia

Surfinia

Grown for their trailing habit, vivid colours and abundance of flowers, making them one of the nation’s favourite hanging basket plants.

Million Bells (Calibrachoa)

Calibrachoa

Million Bells aren’t a member of the petunia family, but they produce tiny flowers like a petunia and have a similar trailing habit to a surfinia.

The Triobell variety of the Million Bells is probably my customers favourite hanging basket plant, but then we are half the price of most local garden centres.

Where To Plant Petunias

Petunia like a sunny position where the soil is well-drained but moist. Avoid a location where water tends to collect after rain or watering as petunias do not tolerate soggy soil.

Watering Petunias

Proper watering will keep your petunias healthily and promotes abundant flowers. Deep watering helps promotes healthy roots, whereas watering lightly and frequently is harmful as the plant grows weak shallow roots. Which inhibits their ability to seek nutrients and moisture in the soil.

Newly planted petunias need evenly moist soil for the first few weeks after planting. Once established reduce watering to once a week, giving them a couple of inches (5cm) of water to moisten the top few inches of the soil.

Petunias can tolerate a mild dry spell but shouldn’t be allowed to dry out completely.

Petunias planted in containers and hanging baskets dry out more quickly than those planted in the ground due to evaporation and limited soil quantity.

Check the moisture levels every day by sticking a finger into the soil. Water when the top inch (2cm) of the soil feels dry. Ensure the soil is evenly watered until the excess drains from the bottom of the container.

Feeding Petunias

Petunia

Once planted start using a liquid feed every two weeks. Spreading petunias may require a weekly feed, while plants in containers and hanging baskets will respond well to a time-released fertiliser.

Petunia Problems

Petunias can be pummelled by the rain which can make them unpleasant to deadhead and can cause grey mould and soft rot.

Slugs and aphids like to eat petunias, opening up sores in the leaves which allow diseases in.

Growing Petunias From Seed

  • Sow petunia seeds from January to April.
  • Petunia seeds are tiny so take care when handling, use a fine seed sower to make things easier.
  • Sow the seeds thinly in trays of seed compost, water the compost before placing the seeds in the tray as watering after may wash the seeds away.
  • Do not cover the seeds with compost as light is required for germination, this is same for begonia seeds too.
  • Place the tray in the warmth 18-25°C and keep moist.
  • Cover the tray with cling film but remove as soon as seedlings begin to emerge.
  • Keep seedlings in a light position but not in direct sunlight.
  • When large enough to handle transplant into trays of potting compost spacing them 2 inches (5cm) apart.
  • Gradually accustom your petunias to outside conditions 2 to 3 weeks before planting in your garden when the risk of frost has passed.

How To Take Petunia Cuttings

  • Take cuttings early in the day when they are full of water, and from non-flowering shoots as they root more easily.
  • Take cuttings around 4 inches (10cm) in length, cutting neatly above a bud on the parent plant.
  • Using a sharp knife trim below a node to make the cuttings around 2 to 4 inches (5-10cm) in length.
  • Remove the lower leaves, pinch out the soft tip and dip the base of the cuttings in hormone rooting powder.
  • Make a hole for the cuttings in a container of cuttings compost using a clean blunt stick, and insert the base of the cuttings with the first pair of leaves just above the level of the compost.
  • Water from above to settle the compost.
  • Cover with a plastic bag and place somewhere warm 18-25°C.
  • Remove the bag to ventilate the cuttings at least twice a week for 10 minutes.
  • Ensure the compost is moist until the cuttings are well-rooted which usually takes around 6 to 10 weeks.
  • Once rooted, harden off the cuttings for about two and pot them on individually.
  • Gradually increase ventilation of the plastic bags to allow the soft leaves to develop a robust waterproof cuticle so that they can survive the lower humidity environment of your garden.
  • Once your cuttings show obvious signs of growth plant them out in your garden.

Petunia Facts

Petunia

Petunias attract hummingbirds.

Petunias are a member of the family of the nightshades, which includes potatoes, tomatoes and tobacco.

Petunias are native to South America, and the word ‘Petun’ is the name for ‘tobacco’ one of its close relatives.

Some types of petunias produce a gooey sap which covers the leaves and protects them from insects and other pests that might harm them.

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