How to Grow and Care For Petunias

Petunias in flower beds and pots are among the most popular annual garden flowers. There are many petunia varieties to choose from; most of them are hybrids. You'll find these prolific bloomers with wide, trumpet-shaped flowers in almost every color but true blue. Colors range from solid to striped or veined, There are petunias with single or double blooms and with ruffled or smooth petals. The branching foliage is hairy and somewhat sticky. The growth habit is mounding or cascading. Some petunia varieties are more fragrant than others. Learn more about how to grow petunias as annuals or short-lived perennials.

Petunias are fast-growing plants that will reach their mature size by late spring. When to plant petunias depends on your area's projected last spring frost date; the plants must not be exposed to any frost.

Petunia Care

Here are the main care requirements for growing petunias:

• Plant petunias in a location where they get at least six hours of full sun per day.
• Make sure the soil is well-draining.
• Protect the plants from extreme heat.
• Water whenever the top 2 inches of soil feel dry.
• Fertilize them regularly throughout the growing season.
• If the variety is not self-cleaning, deadhead spent flowers.

Planting

Plant petunias in the spring when the soil has warmed to at least 60 degrees and there is no more danger of a late frost.

The proper spacing depends on the variety. Multiflora and grandiflora petunias should be spaced about 12inches apart and trailing petunias at least 18 inches apart. Compact Milliflora petunias are planted closer together, about 4 to 6 inches apart.

Light

Most petunia varieties like full sun, meaning at least six hours of direct sunlight on most days. But in the heat of summer, partial shade (especially protection from the strong afternoon sun) will help to keep them refreshed and blooming better.

Soil

Petunias prefer light, fertile, slightly acidic soil (pH between 6.0 to 7.0) with good drainage. Avoid soggy soil, which leads to root rot.

Water

Like many fast-growing flowering annuals, petunias don’t tolerate dry conditions for long periods. Too much water, however, results in leggy plants with few flowers. On average, they need 1 to 2 inches of water per week, more in hot weather. Spreading types of petunias and petunias in pots typically need more frequent and deeper watering. Water whenever the top 2 inches of soil feel dry.

Temperature and Humidity

The ideal temperatures for petunias are roughly 60°F to 75°F during the day and 55°F to 65°F at night, with low to moderate humidity levels. They tolerate temperatures down to about 40°F. Frost and freezing temperatures will damage and ultimately kill the plants in the fall.

Protect the plants from extreme summer heat by moving petunias in pots to a protected area or by setting up a temporary cover over petunias in flower beds. Too much heat can cause a temporary hiatus in blooming.

Fertilizer

Feed petunias at the time of planting with a complete, balanced all-purpose fertilizer. It’s also helpful to work some compost into the soil. Then, starting in July and continuing until the plants decline in the fall, fertilize petunias every two to three weeks with a liquid fertilizer for flowering plants. Some of the spreading types of petunias need weekly fertilization, so be sure to check your plant’s individual care instructions.

Types of Petunias

Petunia varieties are divided into five main groups:

• Grandiflora: These types of petunias have especially large flowers. But they struggle in hot, humid climates. Popular grandiflora petunia series are 'Dreams', 'Ultra', and 'Storm'. A traditional uprightpetuniawith extra-large and showy, bright yellow flowers is 'Prism Sunshine'.
• Multiflora: These petunia varieties have smaller flowers than the grandiflora types, but they make up for it by producing more flowers. They also have a higher tolerance for wet conditions.'Celebrity', 'Carpet', and 'Hurrah' are popular series.
• Floribunda: These petunias are hybrids of grandiflora and multiflora petunias, which share qualities of both types.The 'Madness' series has grandiflora-sized flowers and multiflora weather tolerance.
• Milliflora: The flowers on these compact, miniature petunias are small, only 1 inch to 1.5 inches in diameter, but they are abundant and long-lasting.Popular series are "Picobella' and 'Shock Wave'.
• Trailing/spreading: Trailing petunias have a low-to-the-ground, spreading growth habit. They look great as ground cover or spilling over the edges of containers. 'Wave' petunias grow only 6 inches tall but spread up to 4 feet, making them excellent groundcovers and trailers for containers.

Notable petunia hybrids include:

• Galaxy petunia, also known as Night Sky. The deep purple, trumpet-shaped flowers have white spots dotted across them, creating an otherworldly look reminiscent of the cosmos.
• Supertunia, a series of self-cleaning, abundantly flowering petunias in many different colors from pure white to royal purple.
  

Attract hummingbirds by choosing petunia varieties with red, pink, ororange flowers.

Pruning

When planting young petunias, pinch back the stems to encourage more branching and a fuller plant. How far back to pinch depends on the plant. If it is a short, stocky seedling, just pinch an inch or less. But if the seedling is gangly, pinch the stem back by half.

Petunias often develop leggy stems, which can be prevented by deadheading flowers regularly and pinching back the stems. If this doesn't help your petunias fill out, prune the stems back to 2 to 3 inches long. As the plant regrows, it should be less leggy.

Propagating Petunias

Some varieties of petunias are protected by plant patents and may not be propagated. While it is usually easier to purchase new plants from a nursery every spring, it is possible to propagate petunias from stem cuttings, which takes two to three weeks.

1. In the fall, before the first frost, take a 6-inch cutting from a healthy, green, supple stem. Avoid old and woody stems.
2. Remove foliage from the bottom half of the stem and dip the cut end in rooting hormone.
3. Plant the stem in a small pot filled with damp, soilless potting mix. Place it in bright, indirect light.
4. Keep the growing medium moist. The cutting should root in a few weeks and will grow moderately over the winter. Plant the petunia outdoors after the last frost in the spring.

How to Grow Petunias From Seed

As most petunias are hybrids, you'll have to purchase seeds from a seed company for those varieties, otherwise, you won't get plants that are true to the parent. Start your seeds indoors 10 to 12 weeks before your zone's projected last frost date.

1. Spread the tiny petunia seeds on top of a moist seed-starting mix. Gently press them down, but do not bury them as they need light to germinate.
2. Cover the container with clear plastic and place it in a warm spot but out of direct sunlight. Germination occurs after seven to 10 days.
3. Once seedlings emerge, remove the plastic.
4. When the seedlings have three true leaves, transplant them into small pots and keep them well-watered and in a location with bright light until they are ready to be transplanted outdoors after the last spring frost.

Potting and Repotting Petunias

Petunias make excellent container plants. Use a container with large drainage holes. Any pot material is fine, but opt for a light color to help prevent the roots from overheating. Fill the pot with a high-quality all-purpose potting mix.

Use a container that accommodates the mature size of the plant to avoid having to repot them during their single growing season. Disturbing the roots during the growing season might hinder blooming.For a fuller look, plant up to three plants in a 12-inch container.

Overwintering

Petunias won't survive frost, that's why they are grown as annuals in most places. As bedding annuals like petunias are inexpensive and widely available at nurseries and garden centers every spring, trying to overwinter them indoors is usually not worth the effort.

Common Pests & Plant Diseases

Pests that might bother petunia plants include aphids, flea beetles, budworms, slugs, and snails that feed on the stems and leaves. Often, a strong blast of water washes them off, but if the infestation is severe and impeding flowering, you might have to use an insecticide such as neem oil.

Petunias are susceptible to fungal diseases, such as gray mold, especially in rainy climates. Opt for a variety that has a higher tolerance for moisture if you live in wet conditions.

Unfortunately, petunias are not deer-resistant, so you will have to take measures to protect your flowers from getting eaten.

How to Get Petunias to Bloom

If your petunias aren't flowering, it's usually because the growing conditions aren't right.

Bloom Months

The primary blooming season for petunias is in the summer, though in warm spring they may start flowering in April and stretch into October or whenever the first fall frost occurs in your location.

What Do Petunia Flowers Look and Smell Like?

Petunia flowers are single and funnel-shaped, consisting of five fused or partially fused petals. The flowers of the hundreds of petunia varieties vary greatly in size, shape, and color. The flowers are fragrant, with a sweet, fruity, nutty smell reminiscent of cherries and almonds.

How to Encourage More Blooms

To keep petunias blooming all summer. ensure they get enough sun, water, and fertilizer. Also, deadhead the spent flowers and prune back scraggly, leggy growth in mid-summer.

Older petunia varieties typically need deadheading to continue blooming at their best throughout the summer. However, many newer varieties don’t require deadheading.

Common Problems With Petunias

Petunias are easy-going plants but occasionally you may spot the following issues.

Wilted Flowers or Leaves

There are several reasons for wilted petunia flowers or leaves, but most of the reasons come down to water: too much or too little. Check the soil. If it's not damp, water your petunias. If it's moist, ease up on your watering routine.

Leaves Turning Yellow

Yellow leaves may indicate a lack of nitrogen, not enough sunlight, poor drainage, lack of water, or iron deficiency. Review the growing conditions of your petunias one by one to determine the cause.

From: thespruce