How to Grow Petunias: The Complete Petunia Flower Guide (2024)

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Petunias need full sun, or they will become spindly. They don’t tend to flower wellinshade.

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 soilwith finished compost prior toplanting.

When to PlantPetunias

• It’s easiest to buy young plants from a nursery that sells petunias in flats. Look for plants that areshort and compact. Leggy petunias with tons of flowers already won’t settle in asfast.
• If you wantto grow petunias from seed, start the seedsindoors 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 fromlatefrosts.

How to PlantPetunias

• Petunia seeds are very small (dust-like!) and needlots of light in order togerminate.
• When the young plants have three leaves,plant themoutside.
• Space the plants about 1 footapart.
• If you’re planting petunias in containers, use a container potting mix that will drainwell.

• Petunias are fairly heat tolerant, so you shouldn’t have to worry about watering them frequently. 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 will require more frequent watering than those planted in theground.
• Fertilize petunias monthly with a balanced fertilizer to support their rapid growth and heavy blooming. Double-flowered cultivars enjoy a biweekly dose offertilizer.

What to Do With LeggyPetunias

• By midsummer, most petunias tend to get leggy, producing blossoms at the tips of long, leafless stems. To keep petunias tidy and flowering, weprune the shoots back to about half their length. This will encourage more branching and moreflowers.
• 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 remainingleaves.
• Remove faded, old, or dead blossoms (a practice called “deadheading”) to both improve blooms and attractiveness, especially for the larger-flowered petunias.Deadheading prevents seed pods from competing with blooms for the plant’s food supplies. Clippings can be added to acompost pile to berecycled.

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 areideal forgroundcover.
• ‘Primetime’ series stay compact and uniform, covered with 2¼-inchflowers.
• ‘Heavenly Lavender’ is an early, compact, double, deep lavender blue with 3-inch blooms on 12-to 14-inchplants

Grandifloras

• ‘Sugar Daddy’ (PetuniaDaddy Series), which sports purple flowers withdarkveins.
• ‘Rose Star’ (PetuniaUltra Series), whose flowers look striped because of its rose-pink flowers with awhitecenter.

Floribundas

• ‘Celebrity’ series petunias are compact and rain-tolerant. The flowers reach 2½ to 3 inchesacross.
• ‘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 afterrain.
• ‘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 arainstorm.

Millifloras

• ‘Fantasy’ forms neat, compactmounds.

TrailingPetunias

• ‘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 inchestall.
• ‘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, andheavy-blooming.

Catherine Boeckmann