Growing Petunias

Color your garden with the wonderful world of petunias. These fabulous favorites open flowers in every color but brown. You can find blooms in pale pastel hues, black and even the botanically elusive blue. Newer petunia introductions bring playful personalities to the garden with blossoms boasting one hue ringed in a contrasting shade at the edges.

Petunias are tender perennials in Zones 9-11 but are typically grown as annuals in all zones. Grandiflora types have large blooms and are often used in hanging baskets and pots for maximum impact; multiflora types have more abundant, but smaller, blooms and are typically used in landscaping beds.

How to Grow Petunias

Petunia plants are easy to please and fill containers and planting beds alike with a season-long show.

Planting

Plant petunias whenever they’re displayed for sale at local garden centers, starting in spring. In hottest parts of the country, get petunias planted while days are still cool so they’re fully established before heat arrives. Pinch petunias as you plant to encourage branching.

Soil

There’s no need to spend intense effort on soil prep. These pretty bloomers thrive in average soil as long as it drains well. If your soil is heavy clay, amend with plenty of organic matter or build raised beds to give petunias the drainage they crave. In planting beds and containers, blend a slow release fertilizer into soil prior to planting according to suggested rates on the fertilizer package.

Sun

Full sun coaxes the most flowers out of plants, but you’ll still see a strong show with most types in areas with a little shade for part of the day. With containers, light shade during the hottest part of the day can be helpful, especially as summer wears on and daily watering isn’t enough to slake potted petunias’ thirst.

Watering

Petunias can take summer heat in even the warmest regions, but you’ll need to water plants consistently to keep the flowers coming. In landscape plantings, water spreading petunias, such as Wave or Supertunia types, a few times a week once summer heat arrives. These plants can grow up to a foot a day in ideal conditions, and they need sufficient water to fuel that intense growth. Other petunias can get by with less frequent watering—maybe twice a week in Southern areas and weekly in cooler Northern zones.

Fertilizing

Spreading petunias have humongous appetites. Feed them weekly in planting beds and pots with water soluble fertilizer. Fish emulsion is a good natural choice. In containers, try a bloom booster fertilizer. Look up your petunia type online to learn if you need to remove spent flowers. With many of the newer petunias, plants are self-cleaning.

Maintenance

If petunia plants start looking a little ratty in midsummer, give them a trim. Remove up to 20 percent of total growth—either in length or number of stems. Fertilize plants after trimming to jump-start new growth. Depending on where you live, you might need to repeat the process in late August, especially if petunias usually grow well into fall in your region.