Petunias are one of the easiest flowers to grow for season-long color. They became popular in the Victorian era when they were introduced in Europe in the 1800s and have been brightening up gardens ever since. They’re versatile annuals, available in a variety of colors ranging from pure white to hot pink and everything in between, including stripes and speckles.
These pretty trumpet-shaped flowers look beautiful tumbling out of hanging baskets, window boxes, planting beds, and containers of all sizes. With a mounding or cascading form, they add bold color to your garden all season. Pollinators, such as butterflies and hummingbirds, love them, too. But for the best performance of your petunia plants, there are a few things you should know.
How to Care for Petunias
Petunias are not super-fussy, but they do need proper care to thrive. If you give them the appropriate light, water, and fertilizer, they will bloom for the entire season in most of the country, adding vibrant color to beds, containers, and hanging baskets.
When to Plant Petunias
Petunias don’t like cold ground. “It’s important to plant petunias after the last frost date and when the soil temperature is consistently above 55 to 60 degrees (Fahrenheit),” says Noah Derohanian, Proven Winners director of product management. “Planting at this time allows the roots to establish themselves in warm soil, promoting healthy development.”
Before you plant, consider how different types behave. Petunia plants may have a mounding or spreading/trailing form, depending on the variety. Some types tend to stay more upright and bushy, while others spread up to several feet wide. Read the plant tag or description to understand what you are buying.
Light Requirements—and When Petunias Benefit From Afternoon Shade
Petunias do best when they get 6 or more hours of direct sunlight per day. “In the shade, petunias will grow but they will be leggy, reaching for the sun, and will not bloom well. In very hot climates, such as Texas, planting petunias with a few hours of afternoon shade will help them last into the summer longer,” says Steven Engel, regional account manager for Pan American Seed, maker of the Wave Petunia collection.
Best Soil for Petunias
Petunias thrive in well-draining soil with a pH that is neutral to slightly acidic, says Engel. Incorporating organic matter and compost into the beds with petunias will help improve the soil structure and increase fertility.
How Often to Water Petunias
When watering petunias, pay special attention to the first two weeks after planting, as this stage is critical for their survival, says Derohanian. Water deeply, letting the root ball become saturated. Then let them dry out slightly between waterings.
If possible, water with drip irrigation or water under the foliage. “If petunias are watered overhead and the flowers get too wet, the blooms will not last as long, and there will be a higher chance of Botrytis, which is a disease that causes brown spots on leaves and gray, fuzzy mold on flowers,” says Engel.
Ideal Temperature and Humidity for Petunias
Petunias love temperatures in the 70s and 80s, but if it gets too hot, they will fade. Petunias can be planted in the spring and again in the fall in the warmer zones, says Engel.
While petunias are often grown as annuals, says Engel, “In frost-free zones, petunias could be perennial. However, in the warmer climates, they usually do not make it through the summer heat, especially if there is heat and humidity. In those areas, petunias might be an early spring or late winter flower option instead.”
How to Fertilize Petunias
“Feeding petunias is an important factor in keeping petunias looking good,” says Engel. When planting in the ground, use a water-soluble fertilizer in cool temperatures and a balanced 10-10-10 (NPK) slow-release granular fertilizer in warmer temperatures. Follow the label instructions, reapplying according to the directions.
In containers, feed with a water-soluble type every 10 to 14 days, says Engel.
When to Deadhead Petunias—and When You Can Skip It
It’s not necessary to deadhead most types of petunias. “The plant will continue to set flowers if the plant receives proper sunlight and are healthy,” says Engel. The exception, however, is floribunda types which do better when the spent blooms are removed. It is totally fine, however, to remove any spent blooms any time you like to keep the plants looking neat and tidy. It’s strictly personal preference.
Common Petunia Problems
Overwatering and How to Avoid It
Petunias are relatively easy-care plants, but avoid overwatering. If they get too soggy, this can lead to root rot, says Derohanian. Petunias also can be susceptible to botrytis in wet climates or if kept too soggy. Allow them to dry out between waterings.
Common Pests to Watch For
Aphids, slugs, and flea beetles may occasionally affect these plants. Use a blast from the hose to knock down aphids, hand pick slugs, or use neem oil to manage young flea beetles. The most effective management comes from monitoring and catching problems early.
Petunia Plant Basics at a Glance
Common Name: Petunia
Botanical Name: Petunia x hybrida
Plant Family: Solanaceae
Type of Plant: Annual
Native Origin: South America
Sun Exposure: Full sun (6+ hours of direct light)
Mature Size: 6 to 12 inches tall by 18 to 48 inches wide
Toxic to pets: No
