Petunia: Growing From Seed, Planting and Handling

Petunia is a genus of herbaceous perennial plants and subshrubs of the Solanaceae family. Naturally petunia grows in the tropics of Brazil, Argentina, Bolivia, Uruguay and Paraguay. One variety of petunia you can even find in North America. Actually, the name “petun” means “tobacco” in Latin: tobacco is one of petunia's relatives.

There are about 25 species of petunia known, some of them are really unlike the others. Plant breeders cultivate petunias since the 18th century. Some hybrids were bred a hundred years ago and are still used for growing as annual plants indoors or out. Flower gardeners highly rate petunia for its bright, large flowers that decorate gardens throughout the blooming season: from Summer to first frosts. Therewith, petunia perfectly chords with other garden flowers such as geranium and begonia. There are hanging species of petunia that often grown as a composition of several varieties in a pot, perfectly decorating your house, garden or balcony with colourful hanging flowers.

Another reason of petunia's high popularity is that it's really easy to grow and handle.

  1. 1. About Petunia
  2. 2. Species and varieties
  3. 3. Growing petunia from seeds
  4. 3.1. Sowing
  5. 3.2. Seedlings
  6. 4. Planting petunia
  7. 4.1. When to plant
  8. 4.2. How to plant
  9. 5. Handling of petunia
  10. 5.1. Care tips
  11. 5.2. Propagating petunia from cuttingsSowing
  12. 5.3. Pests and diseases
  13. 6. Harvesting seeds
  14. 7. Petunia after blooming

About Petunia

Petunias are subshrubs, bush alike branchy plants 15 to 70 cm high, with hanging or upright stems. Leaves are mostly ovate, alternate and sessile, 5 to 12 cm long, green or dark green. Stems and leaves often have sticky fine hairs. Flowers are funnel-shaped, placed on short stalks, double or single, regular- or irregular-shaped, sometimes with fimbriate petals. The petals of a petunia flower can be red, purple, white, pink, violet or blue, with brims or streaks. The fruit of petunia is a capsule with tiny seeds.

Outdoors or on balconies mostly grow species of hanging petunia or petunia × hybrida, that were cultivated from petunia axillaris and wild purple petunia.

The blooming period of petunia starts in the summer and lasts until first frosts. Perrenial by nature varieties are cultivated as annual plants.

Species And Varieties

Petunia × hybrida cultivars are split in two groups: multiflora and grandiflora.


Plants of this type start flowering earlier than the plants of the grandiflora hybrids. They produce many small flowers (5 cm in diameter) and have an extensive blooming. Petunias multiflora are easy to care for: they grow in any soil, love sun and are not afraid of rain – the ideal garden flowers. Maybe they look not so chic as grandiflora types, but obviously they are very beautiful. Compact bushes are filled with flowers in all colours and keep blooming until frosts.

Here are some popular cultivars of petunia multiflora:

Fantasy: It's a series of nine hybrids. Plants are 20 x 20 cm with 4 cm flowers in many colour variations:

  • red with streaks and white corolla tube;
  • soft pink with cream corolla tube;
  • salmon-pink with dark streaks;
  • white, crimson, purple-blue, etc.

Mirage: A series of 13 compact hybrids with double flowers 6 to 9 cm in diameter. You can find them in different colours:

  • pink-violet with purple streaks;
  • pink with dark pink streaks;
  • pink with crimson streaks;
  • white, raspberry red, and many others.

Plum crystals: bushes of this type are about 30 cm high and 25 cm in diameter. Flowers are up to 7 cm in size. When just opened up, flowers are pink-violet, then they change colour to soft violet and later on to pale violet. Petals also have streaks which contrast the main colour.


This group of hybrids consists of hundreds of varieties. These plants have large beautiful flowers, although there aren't many blooms on one bush. A big disadvantage of petunia grandiflora is that the flowers are very fragile, so the plant can lose its decorative function because its flowers were damaged by rain or wind. That's why it's recommended to grow gorgeous grandiflora in pots indoors or on balconies and terraces, but not in oudoor gardens.

Grandiflora group is divided on several subgroups:

  • grandiflora/grandiflora low: 60 cm/ 25-30 cm high, flowers are 8-10 cm in diameter, with smooth petals;
  • grandiflora fringed/grandiflora fringed low: 65-70 cm/ 25-30 cm tall, fringed flowers up to 12 cm in diameter;
  • grandiflora splendiferous/grandiflora splendiferous low: 50-75 cm/ 30-40 cm tall with smooth wide flowers with streaks 10-12 cm in diameter.
  • double-bloom grandiflora: 50-60 cm high, with large double flowers, smooth or with fringed edges, 10-12 cm in diameter.

The most popular varieties of petunia grandiflora are:

Hit parade: early blooming hybrids, up to 25 cm tall, with flowers in all colours: pink, raspberry red, white, white star on blue, salmon-pink, purple-blue etc.

Picotee: a series of 4 hybrids, 25 cm tall. Flowers are red, purple, pink, purple-blue, crimson. Petals have ruffled edges with a wide white stripe.

Purple Pirouette: violet-purple double-bloom hybrid, with white brims at the edge of ruffled petals.

Petunia floribunda

This group of petunia stays inbetween multiflora and grandiflora groups. The flowers are very stable and not afraid of rain, just like small flowers of multiflora. But these plants look nice only when being grown in groups, in large flower gardens.

The popular cultivars of this group of petunias are:

Sonja: a bestselling series of 11 hybrids. Small subshrubs are 25 cm high with flowers in many colours: pink, crimson, raspberry-pink with white star, raspberry-red, with white star, red with white brim, white, red, pale-violet with purple streaks.

Celebrity: a series of hot summer and heavy rain survivors. Flower heads are single-,bi- or three-coloured

Hanging petunia

These plants look different from all the other species because of their long, flexible, hanging stems. Petunias of this group are fast growers and rough weather survivors.

Some popular varieties of hanging petunia are:

Surfinia: most plants have flowers 6-9 cm in diameter, although there are some mini-varieties in this series: Pink Mini and Mini Purple, they have small flowers that are 5.5 cm in diameter. You can find them in any colour except for orange and bright-yellow.

Timbelina: Japanese cultivars with double blooms.

Conchita: a series of mini-hybrids with tiny flowers in many colours, 5 cm in diameter.

Growing Petunia From Seed


Often novice gardeners ask how to grow petunia from seed. If you can provide seedlings with extra lighting, then you can start sowing already in February. But usually the best time for setting seeds is the second half of March. Note, that petunia seeds have low germinating ability, so set quite a lot of seeds, to be sure that some will sprout.

Petunia needs loose, light and nutrient-rich soil: 2 parts of hummus and leaf mold, 2 parts of decomposed manure, 1 part of sand and 2 parts of peat.

Always sift the top layer of soil (1 cm). One day before sowing, water the soil plentifully.

Mix the seeds with sand and pour them onto the soil in the container, flatten the soil and spray it well with water. Cover the container with glass or plastic foil and keep at a temperature of 20-23 °C. First sprouts will pop up in about a week, they will need to be sprayed and aired every day.

Your main task during this stage is to provide the seedlings with a high level of humidity inside the hothouse (container). But you'll also need to protect the sprouts from getting black stem disease: every day turn the glass or wipe the plastic foil as soon as you see condensed water vapor on it.

Once a while spray the sprouts with a light potassium permanganate solution instead of water. When your seedlings get their first leaves you can remove the glass, add a layer of sand onto the ground and reduce watering.


When the sprouts get 3 to 4 leaves, prick them off, but first make the ground in the container wet. Carefully guide up a sprout with a stick, and slowly pull it out of soil with its leaf, trying not to shake off the ground. Then transplant the sprout into a peat or plastic pot with the same soil mix.

Water transplanted seedlings and cover the pots for 2-3 days with paper or frost cloth.

During this period you need to care for your petunias very attentively. You need to be especially careful with keeping the soil moderately moist. The watering schedule at this point depends on many factors, so you need to decide yourself how often the soil needs to be watered: 2-3 times per day or 1-2 times per week. Don't forget to loosen the soil around your seedlings.

Start to fertilize your petunias a week after transplanting with foliar and root fertilizers, in turns. Use about 25-35 g of water-soluble complex fertilizer per 10 l of water.

Multiflora species will start blooming 2.5 months after planting, grandiflora cultivars need about 3 months to start flowering.

Before transplanting your seedlings into garden beds, you need to harden them. Keep them in a cool room for a while, and daily bring them outside for a short period of time.

Planting Petunia

When to plant

Petunia prefers sandy loam rich soils. Add some compost or humus into the ground before planting petunias, they will appreciate it. But do not add any manure, it may trigger fungal diseases.

The site needs to be open and sunny. Wait until there are no more frosts and then start panting petunia into the garden soil (in April-May). It's better to plant petunias in the evening or during a grey day.

How to plant

When you are implanting a blooming petunia, it keeps flowering until November. Usually, gardeners plant petunia at the edge of a flower bed, due to its compact size.

Water the seedling and then plant them together with their soil balls 30-40 cm apart. Once planted, moisten the petunias, and mulch the ground the next day.

Handling of Petunia

Tips for caring

Growing petunia doesn't ask a lot of effort, but to reach the best results you need to learn the basics of caring for petunia.

Petunias are mostly hot summer survivors, but they need to be watered plentifully during a hot Summer. Grandiflora species need watering even more than multiflora.

When moistening, be careful not to damage the fragile flowers of petunia. The day after watering, control weeds and loosen the ground: the soil needs to stay soft, without the top layer becoming hard and crusty.

The most important thing, when it comes to handling petunias, is regularly providing them with extra nutrition. Start fertilizing petunias a week after you planted them into a flower bed, and keep fertilizing every 10 days until August with complex, rich of potassium fertilizers. Sometimes you can use organic nutrition, such as fertilizers with humic compounds.

Propagating petunia from cuttings

This is a good way to propagate hanging and double-bloom cultivars of petunia and mini-petunia varieties.

Cutting of double-bloom petunia you need to process in the end of Winter or the beginning of Spring. Cutting of mini and hanging petunias is possible at any time of the year, but assure that you can provide them with fluorescent lamps and temperature of 21-24 °C.

You will need to take from a mother plant cuttings with 4-6 leaves, but only keep the 2 top leaves. Even these last two leaves you need to trim to about half of their size.

Plant cuttings into the same soil mix you would use for seeds, but with a 2-2.5 cm layer of sand on top, moistened with a fungicide solution. Plant cuttings 1.5-2 cm apart and cover the container with glass.

You don't need to use growth enhancers. It's more important that the cuttings are fresh: they lose their rooting ability with every minute.

Assure that the soil in the hothouse is moist, and spray your cuttings with water twice a day. But make sure that it's not too humid inside the container, otherwise there will be a risk of mold or black stem disease.

When the roots of cuttings become 1 to 1.5 cm long, individually replant them in pots (5 cm in diameter).

To make your plants more branchy, nip the seedlings above the 4th or 5th leaf. You can also use the resulting cuttings for rooting. If needed, after 2 weeks nip the sprouts again.

After 1.5 months transplant the sprouts into the bigger post (11-13 cm in diameter).

Handling requirements for petunia cuttings are about the same as for seedlings, but mini and hanging species require more room to grow, so you will need to hang the pots up.

Pests and diseases

If you care for your plants correctly, there will be no risk of pests or diseases. But things happen, and one day you might notice that your petunia is getting dry or yellow.

When petunias receives bad care, it can get foot rot disease or chlorosis, black stem or botritis disease. To control them you can buy a special treatment, but it's a lot easier just not to let it happen.

There is also risk of viruses and predators. Petunias can be attacked by red spider mites, plant lice, slugs, thrips: in this case use insecticides to control them.

Harvesting Seeds

If you would like to collect seeds from your petunia plants, wait until they are completely ready. Choose the species that you like the most, and investigate a few flower buds at the bottom (they make seeds faster). Two months after the flower bud has formed, the seeds will be ready to harvest.

Seeds of petunia are very tiny, about 0.5 mm in diameter. There are around a hundred of seeds in one capsule. You can cut them off and store them at home, but it's better that you take the seeds out of a capsule and put them in small bags with the name of species and the year of harvest on them.

The seeds still need about 2 months to be completely ready. If you store them correctly, they will keep their germinating ability for 4 years.

Petunia after blooming

When your petunias have thrived off, but you want to keep some very special variety at home, dig it up in October, cut the stems and plant it into a pot. Place the pot into a cool room where your petunia will rest. Keep the soil in the pot moderately moistened.

Around February, move your petunia into a warm room and place it at the window. Start regularly to water the plant, and soon you will see new sprouts.

When the sprouts get 3 pairs of leaves, you need to cut them and let them root in a pot with rich soil that has a layer of sand on top. Cover the pot with glass and put it in the semi-shade. For the next 3 weeks water, air and spray your petunias when needed, until the sprouts get roots. Then you can replant them into small pots and let them grow there, until it's time to move the seedlings into flower beds outdoors.

Surely it's a lot easier to buy new seeds every year and grow petunias as annual plants. Just remove old plants from a flower bed and turn over the soil.

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