Petunia care: expert tips on watering, pruning & more

Sabine
Sabine
Sabine
Sabine

I am currently studying agricultural and food economics. As a keen hobby gardener, plants take up most of my free time. A few years ago, I got especially interested in herbs, which is why I completed my studies to become a certified herbalist in 2018.

Favourite fruit: apples, cherries
Favourite vegetables: potatoes, fennel

With proper care petunias will delight you with their strong flowering power. We show what you should bear in mind when caring for and overwintering petunias.

Multi-coloured petunia flowers outdoors
Petunias add bright accents of colour to your garden [Photo: Ozgur Coskun/ Shutterstock.com]

Petunias (Petunia) are among the most popular bedding and balcony plants. This popularity is not only due to the enormous diversity of the different varieties in terms of flower colour and shape. The flower is also easy to care for and can be very resistant to diseases and pests. In this article we have compiled a few valuable tips for the care and proper wintering petunia, so that every year you can enjoy the colourful flowers from the beginning of June until the first frost.

Petunia care

Petunias are undemanding fellows. But even with these natural beauties, the right care decides whether the plants achieve visual excellence.

Watering petunias

Petunias need not only a lot of sunshine, but also a lot of water to thrive. In particular due to the special demands on the properties of the irrigation water, it is necessary to consider a few things in the watering of petunias: The plants are generally quite tolerant of short-term drought. Watering should always be from the bottom, so that the leaves do not become stuck with the glandular hairs located on it. If the water from the tap is too hard, it helps to boil it for a few minutes before watering. This causes the minerals that make the water hard to be precipitated. However, before pouring, the water must be cooled down to room temperature again.

Note: the availability of iron is best for plants in acidic soils with a soil pH of 4.5. As the pH value increases, the availability decreases. Hard water makes the value in the root zone of petunias increase due to the minerals it contains, so it is better to water with soft water. If necessary, a liquid iron fertiliser can be used.

How to properly water petunias?

  • Water generously, but avoid waterlogging
  • Water from below
  • Use soft tap water or rainwater
A white-speckled purple petunia
Petunias need sufficient water to produce abundant flowers

Fertilising petunias

To grow vigorously and produce many flowers, petunias need to absorb plenty of nutrients from the soil. With a need-based fertilisation, you can support your plants in their development and in return enjoy a lush bloom throughout the year. To ensure perfect starting conditions, it is best to add rich compost or potting soil to the planting hole at the time of planting. In addition, it makes sense to immediately incorporate a fertiliser with a long-term effect, such as our Plantura Flower Food. This ensures an optimal start at the new location and provides the plant with all important nutrients.

Person deadheading a petunia plant
Pruning wilted petunia blooms prolongs the plants’ flower period [Photo: FotoHelin/ Shutterstock.com]

Pruning petunias

Faded flowerheads should be removed regularly to prevent mould growth. In addition, removal prolongs the flowering phase, as this inhibits the formation of seed pods. Your petunias can then use the saved energy for the formation of new flowers and shoots. If you want to overwinter your petunias, before and after overwintering, carry out a radical pruning of the shoots to about 15 centimetres.

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Overwintering petunias: What to look out for

Most petunias that are commercially available here are annuals. They bloom from June until the first frost in the most beautiful colours, but after a year in the spotlight, they usually disappear into the depths of the rubbish bin. But if you do not want to let your most beautiful specimens die, or would rather invest your money next year in something other than in new petunias, you can get your plants through the winter (September/October). By the way, this works especially well with petunias in the ‘Sufinia’ series.

Preparing petunias for winter

Without much effort, however, does not mean no effort at all. To ensure your petunias can be successfully overwintered, you should move them to suitable winter quarters before the first frost (September/October). In addition, you should cut all non-woody shoots to a length of about 15 centimetres.

Petunia care during winter

Even during the winter dormancy, it is necessary to pay attention to some aspects in the care of petunias. It is best to overwinter your petunias in a bright, cool room at about 5 to 10 °C. The ideal location should also be protected from draughts and dry heating air. You only need to water a little during hibernation. However, the petunias should not dry out completely. Fertilisation is not necessary over the winter, but you should check the plants regularly for infestation with pests – such as aphids (Aphidoidea) – so that you can react quickly if necessary.

Aphids on a green stem
Petunias can fall victim to pests such as aphids [Photo: HHelene/ Shutterstock.com]

Petunias after winter

After a blissful hibernation, petunias cannot go outside again straight away. Cut back the new shoots again in the spring to encourage new growth and better branching of the shoots. Then, from February-March, you can begin to acclimatise the plant and water it more. However, at night and on days that are too cool, it is better to put your petunias back on the warm windowsill. Also, now is the best time for repotting. To do this, generously remove the old substrate from the roots and place the plant in lukewarm water for about 15 minutes. Next, select a large enough planter and fill it with fresh, nutrient-rich substrate before replanting your petunia. If there is no longer a danger of frost, you can then plant your petunia outside again from mid-May.

Tip: if you want to enjoy a lot of new petunias or simply do not have space to overwinter the plants, collect the seeds of these sun-hungry flowers in the autumn. We have put together information on how propagation of petunias via seeds works here.