Planting, Growing, and Caring for Petunias
Pretty petunias are popular because of their exceptionally long flowering period. As with most annuals, they get leggy by midsummer, so you’ll want to prune the shoots back by half. See more tips on planting and caring for 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 ground covers. 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 ground cover. They can be used in window boxes or hanging baskets.
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Planting
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.
Types
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 are 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 mounds.
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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Is you petunia outdoors? The plant doesn't get as much sunlight in the winter months so if possible move it to a spot where it gets maximum sun. Give the petunia some fertilizer and remove all spent blossoms.
Aye, Ian!
Our sources suggest that petunia are long-day plant that flower under any photoperiod. Short periods delay flowering and tends to result in "stretched" plants. See comments (answers above) for growing under florescent lights. Consider, too, night temps of 60°F to 63°F and daytime temps of 70°F to 75°F. Good luck with this—and thanks for asking from so far!
It's fine to plant petunias in the same soil next year. Just add some well-rotted manure or compost before planting.
Petunias are great in the vegetable garden. They repel aphids, asparagus beetles, leafhoppers and tomato worms. Some plants that thrive with petunias as companions are basil, beans, tomatoes, corn and peppers. Roses and petunias also grow well together.
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!
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