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

Hi, Erin, You've pretty much

Hi, Erin, You've pretty much figured out the problem. It's the heat, yes, but the time of year—that is, the length of day—plays into it, too. Petunias best days are in the spring, before temps top out and as days get longer. You can read more about them here, on a page by the Alabama Extension service: http://www.aces.edu/pubs/docs/...

How do I mix biotin for

How do I mix biotin for feeding my petunias?

Thank you!

Hi. This summer I planted

Hi. This summer I planted petunias in several containers. They are doing well except one of my containers. My petunias are getting leggy and seemed to be coming out of the soil. I notice the soil is still wet. Why is my my petunias look legggy and what can i do to save my petunias in my containers. Please help.

Many regular petunia

Many regular petunia varieties do get leggy if they're not trimmed. Very common. To avoid this: Every 10 days, cut one-third of the stems back.
If it's more extreme, you can always clip all the stems down to 6 inches down, and fertilize the plant. In about a week, they'll recover and bloom.

My petunia flowers are

My petunia flowers are getting smaller and the flower itself is curling backwards. How can I stop this?

If your petunia flowers are

If your petunia flowers are curling, it probably means a fungus is getting started. Water less, avoid overhead watering and water only at the soil level, increase air circulation, and spray with an all-purpose fungicide.

My petunias stay small and

My petunias stay small and they look horrible they have good soil and I fertilize them and Water them and they just don't grow but they want to bloom and I do cut the stems off

It sounds like you are on top

It sounds like you are on top of the watering situation. Hopefully, they are getting enough sun. Try cutting them back, which will encourage bushier growth. Petunias are heavy feeders and grow best with a soil pH between 5.5 and 5.8. With a higher soil pH, petunias begin to suffer from iron deficiency. Try fertilizing with a fertilizer rich in iron.

Hi all petunia lovers, I

Hi all petunia lovers,

I planed my wave petunia (which said it can spead out 3-4 feet) for 2 months and can't wait to see it spill down from my deck but it has not. When I first grow i headdead them and they bloom like crazy but they don't spill down. My husband said since I headdead them the plants focus on producing more flower and won't grow long, is it true?
Thanks!

My petunias are in a hanging

My petunias are in a hanging basket and are in full bloom. The flowers are fine but I've noticed lately the leaves are turning yellow, especially at the base of the container. They weren't doing this for the first month or so, but it seems to be getting worse now that the weather is warmer. Any suggestions? Thanks.

Have you given your plants

Have you given your plants any fertilizer? Petunias are heavy feeders and grow best with a soil pH between 5.5 and 5.8. With a higher soil pH, petunias begin to suffer from iron deficiency. Try fertilizing with a fertilizer rich in iron.

I have multiple colors and

I have multiple colors and types of petunias in about 15 pots/window boxes that I purchased from a hardware store. Once I got them home, I quickly saw that the flowers were being eaten by something. I do not find any evidence of bugs or caterpillars, but have been spraying the plants daily with Safer caterpillar killer.
I also deadhead the flowers that are affected, but I am not seeing an improvement. What is going on with my plants and how can I treat it?

Hi Debbie, You probably have

Hi Debbie,

You probably have some night visitors. Go out after dark and check for earwigs or slugs. They usually hide during the daytime and come out when it's dark.

Some of the branches in my

Some of the branches in my Purple Wave petunia are sprouting blooms that are a mottled green and purple, almost tie-dyed looking. Is that normal, or a sign of a mutation? Or maybe even a deficiency?

Hi, Sara: Unfortunately, you

Hi, Sara: Unfortunately, you are describing a classic case of tobacco mosaic virus in petunias. This is usually caused by the plants being handled/touched by someone who uses tobacco products somewhere in the supply chain, whether grower, greenhouse, or garden. In any event, there is no cure other than to very carefully (so as not to contaminate elsewhere) and thoroughly remove/destroy the infected plants, soil, and anything else nearby. Sorry!

I am attempting to grow

I am attempting to grow petunias for my wedding in August. I bought some beautiful hanging baskets at mother's day because they were the perfect color. They have gotten very large and I would like to continue to keep them healthy. Does anyone have any advice on how to do this? Will they even stay alive that long?

I'm not a gardening expert in

I'm not a gardening expert in any way, but my own petunia hanging basket has probably tripled in size since I bought it. I had good luck with splitting up some of the plants and re-potting them so they could continue to grow. We put half of them back in the basket and the other half in a big pot and everyone seems to be adjusting well to the move. I'm not sure how long they will last, though. You could try trimming them back if they're too big/long and they should continue to produce new blooms. Good luck and congratulations!

Fertilize your plants monthly

Fertilize your plants monthly to ensure good growth. Also, remove faded or dead flowers to prolong blooming.

I have over wintered the same

I have over wintered the same hanging petunias for the last two years. I did lose a couple of plants the first time around, possibly due to over crowding. I just started bringing the basket in at night, when the temps outside got colder. Once day time temps got cold, they just stayed inside in my sunniest window. I water at least once a week and give them a bit of plant food when I think of it. The plants will bloom less or not at all during the winter, but once the days lengthen flowering resumes.

I just transplanted some

I just transplanted some petunias and begonias into the same pot about two months ago. They seem to be growing very rapidly and are loving the weather. I was just wondering if I needed to take the begonias out soon and if they would be taken over by the petunias???

If you like the combination

If you like the combination of petunias and begonias you can move them all to a bigger pot and keep them together. The begonia will probably get bigger and start shading the petunias in the smaller pot.

How do I know when my

How do I know when my petunias have out grown the pot their in? Thanks Tami

How do you know if plant

How do you know if plant needs bigger pot

If your petunia needs water

If your petunia needs water more frequently than before, if it seems to be top heavy in its pot, or if its roots are growing out from drainage holes in the bottom, your petunia may need to be repotted in a larger pot.

When first planted should you

When first planted should you dead head all the flowers? That's what my Mother used to tell me. Thanks.

Hi, Barbara: Mother was

Hi, Barbara: Mother was always right. Especially around Mother's Day. Uh, actually, come to think of it, Mother was always right all the time. But anyway: Normally, you deadhead the spent blossoms to prevent your plants from becoming scraggly as they put their energy into forming seed pods. When first planting, it's not necessary to deadhead all of the flowers, but what your Mother knew was that doing so would indeed help the plants get off to a good start by focusing their energy on growing. Everything else being equal, they might make out fine without premature deadheading, but perhaps they would do a little better with. Up to you!

I plant petunia in my ceramic

I plant petunia in my ceramic window "boxes", which are about 2ft long, and not wood. They do well in an average potting soil being watered about once every 4 days here in Texas. Any flowers or plants in hot, arid areas need to be watered more often than plants that are in the ground. The heat causes the moisture to evaporate much quicker from pots and planter boxes.

My mother grew petunias

My mother grew petunias successfully and told me to pinch the back the wilted/dead flowers to encourage blooms. Was she correct? If so, do I pinch ony the dead blossom or or behind it, which would include the calyx and so preclude seeds from
forming. She planted anew each spring and not from seeds. She has gone now and you would know best anyway. Advice?

Pinch or cut them back to the

Pinch or cut them back to the first set of leaves or almost to the branch the flower stem came from, which ever is first. If the plants are young pinch back some of the growth tips, it will make the plant grow fuller instead of getting leggy. They usually start getting leggy is you don't deadhead (cut spent flowers off).

I love to plan petunia in the

I love to plan petunia in the window box on my deck. What kind of petunia should I choose to make it trailling cascading down from my deck few feet long and fully bloom?

Thank you.