Growing Petunias

How to Plant, Grow, and Care for Petunias

Often grown as annuals, petunias are one of the most popular flowers because of their long flowering period. As with most annuals, they get leggy by midsummer, so you’ll want to prune the shoots back to about half their length. See how to plant and take care of your petunias to keep them blooming.

Pretty petunias are treated as annuals in most areas but also as tender perennials in Zones 9 to 11. The flowers come in many colors and patters, and bloom from spring until frost!

These colorful annuals can really add pop to a front lawn and often used as borders, containers, hanging baskets or even seasonal groundcover. Some even have a slight fragrance.

Height can vary from 6 inches to 18 inches. Spread can be from 18 inches to 4 feet.

Petunias are divided into different groups, mainly based on flower size:

Multiflora petunias are the most durable and prolific. They have smaller, but more abundant flowers and are ideal for summer bedding or in a mixed border (because they are more tolerant to wet weather).
Grandiflora petunias have very large flowers and are best grown in containers or hanging baskets (because they are more susceptible to rain damage). Theese large petunias often do not fare as well in the south because they’re prone to rot during humid, hot summers.
Floribundas: Floribundas are intermediate between the grandiflora and the multiflora groups. They are free-flowering like the multiflora varieties and produce medium-sized blooms.
Millifloras: Milliflora petunias are much smaller than any other petunias on the market. The flowers are only 1 to 1½ inches wide, but they are prolific and last all season!
Spreading or Trailing Petunias: These are low-growing but spread as much as 3 to 4 feet. They form a beautiful, colorful groundcover because the flowers form along the entire length of each stem. They can be used in window boxes or hanging baskets.

Planting

Petunias need full sun or they will become spindly. They don’t tend to flower in the shade.
They are quite versatile, growing in different types of soil, but it is important that the soil drains well and doesn’t stay wet.
You can grow petunias from seeds, but it is easier to grow them from transplants. If you are going to grow from seeds, start them indoors about 10 weeks before you want to set them outside. Petunia seeds are very small (dust-like!) and needs lots of light in order to germinate. Remember to water them. When the plants have three leaves, you can plant them outside.
It’s best to buy young plants from a nursery which often sells petunias in flats. Look for plants that are short and compact, not leggy and not yet blooming and they’ll settle in faster.
Plant after the last spring frost. (See your local frost dates) in a place that is sheltered from wind exposure. Keep well watered.
Space the plants about 1 foot apart.
If you’re planting petunias in containers, use a soil-less mix.

Care

Petunias are tolerant of heat so you don’t have to water them regularly. A thorough watering once a week should be sufficient (unless there are prolonged periods of drought in your area). Avoid watering shallowly as this encourages shallow roots.
Note: The spreading types of petunias and those in containers require more frequent watering.
Fertilize petunias monthly with a balanced fertilizer to support their rapid growth and heavy blooming. Double-flowered cultivars like a biweekly dose of fertilizer.

Getting Leggy in Midsummer

By midsummer, most petunias get leggy, producing blossoms at the tips of long, leafless stems. To keep petunias tidy and flowering, we prune the shoots back to about half their length. This will encourage more branching and flowers.
After pruning, fertilize and water the plants well to force out new growth and flowers. The plants may look raggedy at first but they’ll rebound with more color and blooms.
- Older garden petunia plants can be pruned prune hard (within a few inches of the base) to re-encourage vigor, especially in cooler climates, but keep the remaining leaves.
Also, remove faded, old, or dead blossoms to both improve blooms and attractiveness, especially for the larger-flowered petunias. Dead-heading prevents seed pods from competing for the plant’s food supplies. Clippings can be added to a compost pile to be recycled.

Pests/Diseases

Petunias have few serious insect or disease pests. Avoid wetting the foliage and flowers when watering to help prevent disease.

Aphids
Slugs

Recommended Varieties

Multifloras

‘Carpet Series’ is very popular. They are compact, early blooming with 1½-to 2-inch blooms that come in a wide variety of colors, and ideal for ground cover.
‘Primetime’ series stay compact and uniform, covered with 2¼-inch flowers.
‘Heavenly Lavender’ is an early, compact, double, deep lavender blue with 3-inch blooms on 12-to 14-inch plants

Grandifloras

‘Sugar Daddy’ (Petunia Daddy Series), which sports purple flowers with dark veins.
‘Rose Star’ (Petunia Ultra Series), whose flowers look striped because of its rose-pink flowers with a white center.

Floribundas

‘Celebrity’ series petunias are compact and rain-tolerant. The flowers reach 2½ to 3 inches across.
‘Madness’ series petunias have big, 3-inch flowers in many veined and solid colors. They are compact and bloom until frost. They bounce back well after rain.
‘Double Madness’ petunias are compact and floriferous with big, 3-inch flowers all through the summer. Like their single counterparts, ‘Double Madness’ petunias bounce back within hours of a rainstorm.

Millifloras

‘Fantasy’ forms neat, compact’Fantasy Pink Morn’, a milliflora type petunia.

Trailing Petunias

‘Purple Wave’ was the first cultivar in the class of spreading petunias. It produces large blooms of deep rose-purple. It is tolerant of summer heat, drought and rain damage. ‘Purple Wave’ remains under 4 inches tall.
‘Wave’ series petunias are available in a multitude of colors. Most are not quite as ground-hugging as the original. They are weather-tolerant, disease resistant and heavy-blooming.

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Reader Comments

Can I transplant my petunias

Can I transplant my petunias from my outside containers into new ones in the house for the winter. I live in Ohio my petunias are thriving and I don't want them to die. So I thought if I repotted them in a good mixture of soil and fertilizer keep them warm and loved that I may keep them growing all year. Do you think that's possible?

Hi Karen, Petunias can

Hi Karen,
Petunias can overwinter indoors but you need to give them lots of light (a south-facing sunny window may work) and add some humidity to the indoor air. Put gravel in a plastic tray and add water. Then place your pots on the gravel. The petunias may still get leggy and stop blooming. You can also take some cuttings from the mother plant and start these indoors. Good luck!

do these flowers come back

do these flowers come back everyyear?

Most people grow petunias as

Most people grow petunias as annuals so they grow just once a season.
In terms of "true" annuals versus tender perennials: True annuals germinate, flower, set seeds and die during one season regardless of which zone they are in (e.g, marigolds are true annuals). Many bedding plants that are sold as annuals are actually tender perennials and will grow as perennials in warmer climates.
Petunias are sometimes also called "hardy annuals".

Actually, petunias are

Actually, petunias are classified as tender perennials grown as annuals. In a mild climate, they will over-winter.

My Petunias have been coming

My Petunias have been coming back every summer, even after this cold winter in Boston. They appear as small plants, like weeds all over the place. They even grow out of cracks between my stone walkway.

I have a number of petunia

I have a number of petunia plants in their 2nd year and they appear to be healthy and have a number of blooms coming. I live in the LA area and we have had a very mild winter!

Every fall my petunias get

Every fall my petunias get small black specks on them similar to poppy seeds. I always assumed that this was eggs of an aphid like bug, but spraying the plants only results in killing them. Is it possible that this is actually the plant trying to reseed itself? I can't find this mentioned in any of my gardening books. Thanks.

Black specs might be

Black specs might be "frass"...caterpillar poop. You may have a worm eating your plants. Blast the leaves with insecticide spray.

i have "poppy seed like"

i have "poppy seed like" specs on my petunias too.. i read that it is called "peroxyacetyl nitrate" (PAN), caused by air pollution. what i read said there is nothing that can be done. i'm not happy with that diagnosis, so i'm still looking

I have two very large

I have two very large containers of petuinas. They have stopped blooming but otherwise look very health. Could they be getting too much water. They are watered by a sprinkler system twice daily.

If your petunias have stopped

If your petunias have stopped blooming (or slowed down), you can try to revive them by clipping the stems back by two-thirds and fertilizing. You could clip all at once, or clip a third every week or so. Your plant may start flowering in a few weeks.
In general, you could clip some of the stems every week to keep your plant healthy and full; also keep fertilizing if the plants are in containers.

Is it really best if I will

Is it really best if I will plant the petunia seeds in a soil less media like carbonized rice hull and vermicast?

If you're planting seeds

If you're planting seeds (versus transplants), clean, damp potting soil is fine.

What is eating my petunias at

What is eating my petunias at night..entire bloom but only the red ones, they dont touch the purple ones?/

Its slugs! I have this

Its slugs! I have this problem every year but mine arent picky! They the purple ones too!

yes how can u see when its

yes how can u see when its going to seed

The flower of the petunia

The flower of the petunia needs to naturally die, and fall to the ground. Then the plant's calyx, the bulging part of the stem below the flower's base, will begin to swell and turn brown. After a period of a couple of days or so, the calyx will split open and the seeds will fall out.

The petunias in my flower box

The petunias in my flower box develop white spots on the flowers the second day of blooming. What causes this, and what can i do to control the condition? Those in hanging baskets do not suffer the same fate.

Did you fertilize your flower

Did you fertilize your flower box? This sounds as if they have fertilizer burn. Make sure you keep fertilizer off the plants and that you water it in well or it's watered down.

My flower look heathy but the

My flower look heathy but the stems are all dried out and looking horrible so the plants looks like there dead what should I do the get all day sun and I water regularly ??

I'm having the same problem!

I'm having the same problem! They were full and beautiful, but now have dried leaves and very sparse. I've watered, cut back on watering and I've also fertilized. I'm at a loss! (I live in Oklahoma - hot, windy, humid)

Any updates? My petunia beds

Any updates? My petunia beds are doing the same thing and it's only getting worse. Help!

Try cutting them back a bit.

Try cutting them back a bit. Also, a thorough watering once a week should be sufficient (unless there are prolonged periods of drought in your area).

There are many differing

There are many differing opinions on whether or not you need to "deadhead" the newer varieties of petunias. What is the real scoop - deadheading is still vital or no longer needed?

For petunias, we would allow

For petunias, we would allow the plant to bloom and re-bloom naturally, then prune backlong branches as the season progresses for renewed flowering.

We are having massive amounts

We are having massive amounts of rain in western Wisconsin this summer (it's June)It has rained nearly every day for the last month. Not much heat for the petunias. They are already going to seed! I have been growing petunias since I was a child and this is truly the first time I've ever had trouble with them. I normally would be getting another 3 months worth of blooms from these guys. Should I cut them way back? We deadhead like crazy-is that the problem? No signs of rot or bugs so we ruled that out! Yikes! I won't get my yearly petunia fix if they stop blooming and seed out!

You should allow the plant to

You should allow the plant to bloom and re-bloom naturally, then prune back long branches as the season progresses for renewed flowering.

I live in southern

I live in southern california. I have planted petunias in pots. But they are not blooming. The plants themselves look healthy but they don't seem to be blooming. I read where you suggested they be given a natural fertilizer biweekly. I've been giving them a 5-5-5 organic allpurpose fertilizer. Should I up the number? Also it gets up to 95-105 degrees so I water every day. Should I not be watering that much? They are in full sun for up to 5 hours. Do they have a blooming cycle?

Cut back on the fertilizer

Cut back on the fertilizer (only fertilize once a month during the hot months) and let the soil dry before you water again. Water deeply but less often.