Sign up for our daily newsletter to get gardening tips and advice.
Planting, Growing, and Caring for Petunias
Pretty petunias are one of the most popular flowers because of their exceptional blooms and 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.
About Petunias
Petunias are treated as annuals in most areas but can be grown as tender perennials in Zones 9 to 11. The flowers come in many colors and patterns and bloom from spring until frost!
These colorful annuals can really add pop to a front lawn and are often used in borders, containers, hanging baskets, or even as seasonal groundcovers. Some even have a slight fragrance. Their height can vary from 6 inches to 18 inches, and they can spread along the ground anywhere from 18 inches to 4 feet.
Types of Petunias
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). These 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 multiflora groups. Like the multiflora varieties, they are free-flowering 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 and can spread as much as 3 to 4 feet. Because the flowers form along the entire length of each stem, they form a beautiful, colorful groundcover. They can be used in window boxes or hanging baskets.
Petunias need full sun, or they will become spindly. They don’t tend to flower well in shade.
The soil should drain well and not stay overly wet, especially in containers. It should also be moderately fertile to promote the best growth. Amend poor soil with finished compost prior to planting.
When to Plant Petunias
- It’s easiest to buy young plants from a nursery that sells petunias in flats. Look for plants that are short and compact. Leggy petunias with tons of flowers already won’t settle in as fast.
- If you want to grow petunias from seed, start the seeds indoors 8 to 10 weeks before your last spring frost date. (See your local frost dates.)
- Plant young petunias outdoors after your last spring frost date, but keep a close eye on the weather forecast and protect young plants from late frosts.
How to Plant Petunias
- Petunia seeds are very small (dust-like!) and need lots of light in order to germinate.
- When the young plants have three leaves, plant them outside.
- Space the plants about 1 foot apart.
- If you’re planting petunias in containers, use a container potting mix that will drain well.
Catherine Boeckmann
ADVERTISEMENT
I’m in my 70 and never had seaside petunias before. So thanks for the advice on how to grow and water them in a pot.
We are so happy to hear that our Petunia Growing Guide was useful! Hopefully, you have gorgeous petunias this summer.
Earlier this season I found a beautiful Black Petunia and it was just gorgeous! It bloomed and did well for a few weeks and then it just drooped and seems to be dying. I would love to know if there is some way I could revive it.
Your black petunia sounds like it had a great start to the season. Drooping and/or wilting can happen for a variety of reasons, most often with either too much or too little water.
Petunias are rather drought and heat tolerant, and do best with a thorough watering once a week. The key is for good drainage because excessive water in the soil can cause the roots to be affected. They prefer slightly moist soil to dry soil, so check your soil to see where things stand before adding more moisture.
If your plant does not perk up when watered, stop watering it and allow the soil to dry thoroughly. Petunias also benefit from a dose of balanced fertilizer monthly.
Drooping can also be due to a lack of sun, as they prefer full sun, or a sign of insect or fungal issue.
I was so relieved to come across Alicia's comment regarding withering petunias. She has described exactly what has happened with my petunias this year!! Exactly!! I have not been able to determine the cause of this problem either. Could there have something in the potting soil used at the greenhouse? I would really like to know the cause so as not to duplicate the problem next year. Nearby flowers don't seem to be negatively affected.
I have successfully grown petunias for many years. I put them in pots on my front steps as well as in the flower beds on either side of the steps, all in full sun. Last year however, they failed miserably. I planted around 60 plants from six-packs over a 3-4 week period. Some died within a week of planting, some after a couple weeks, some after several weeks or even two months. All went through the same stages: one day the plant would look vigorous and healthy; but the next day, the leaves would look wilty - the same look as when water is needed, but water was not needed as the ground was adequately moist; the third day the plant would be withered completely. One by one, the petunias went through these stages until I had only one that made it through most of the summer. This summer, after 4 weeks in the ground, the same thing is happening. I am losing plants daily. I can find no evidence of pests nor of gophers (though gophers would not be able to bother the potted plants). I have kept the soil moist but not wet. I thought that perhaps there was something wrong with my soil, but the petunias in pots with potting soil were/are dying just the same way as those in the soil. I'm completely baffled. As I said, I have successfully grown petunias for many years. I will appreciate any insight given. Thank you.
Hello, I had gorgeous “Galaxy Petunias” that were mainly purple in color with speckles of white. This last bloom all the flowers came out fully white with the only purple being in the bottom of the buds (closest to stem). Can anyone tell me why this happened and what I can do to get my flowers back to their prior glory? Thank you in advance.
Color changes in flowering plants is something of a mystery. It could be from limited chlorophyll or another component of photosynthesis. Some sources also suggest that temperature plays a role.
If anyone has other explanations we’d love to hear them!
I've just moved from 6b planting zone to 9a. I've had 6 large planter pots across my back deck in full sun with petunias at both of my homes. In the 6b zone I would plant them from 4-6 inch pots or flats on June 15th (never before) after, hopefully, the last snow. They would bloom beautifully all summer long with minimal care needed; a little dead-heading, a couple miracle-grow shots. The pots would fill abundantly with lovely multi-colored flowers hanging all the way to the ground by mid July. Stunning! Bloom would usually be done by mid to end of September with the first cold bite. My new home this year in 9a. It's been a continual fight of aphids all summer long every 2-3 weeks with soapy water, store-bought remedies...I've tried everything. After each treatment, the plants lost their blooms and would look bare for a week or two, then abundant blooms would appear again (with aphids). It was cyclical. It's Nov 20th in 9a zone. We've had several frosts and the flowers and leaves still look good. I've read petunias may be perennial in this zone. We'll see. If they do, I may keep them, otherwise, any ideas on another full sun flower that doesn't have the pest problem?
I found Dr. Doom took care of the aphids. Works great on the ant problem as well. Hope this helps.
