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How and When to Plant Petunias

If you are looking for plants with versatility and magnificent, prolific blooms that keep performing all spring and summer long, petunias will not disappoint. As long as you know how and when to plant petunias, these much-loved annuals are vigorous producers of vibrant flowers throughout the growing season and can be planted just about anywhere as long as they receive adequate care and lots of sunlight.

There are so many reasons to fall in love with petunia plants, from their abundant varieties and varying growth habits to their festive displays of blooms. Check out our detailed guide that is full of tips on how to plant petunias so you can enjoy the rewards of their show-stopping splashes of color.

Petunia flowers that are growing in a garden.

Ideal Soil Composition & pH for Growing Petunias

Petunias enjoy a light, fertile, well-draining soil. A premium potting mix is ideal for growing petunias in hanging planters or pots. When learning how to plant petunias in the ground, remember to amend your native soil with plenty of organic matter and well-decomposed compost.

Petunia plants grow best when the soil is slightly acidic, with the target being 6.0 to 6.5 on the pH scale. If you are unsure of your soil quality or pH, visit your local extension office with a soil sample. The experts will break down what kind of soil you have and give suggestions on what soil amendments are necessary for peak growing performance.

Petunia Light & Temperature Requirements

Petunia plants are warm-season annual plants that crave sunshine. Plant petunias in full sun so that they receive a minimum of 6-8 hours of direct sunlight per day. They will tolerate partial shade but will likely not produce blooms as profusely.

  • Petunias love sunshine, but too much intense heat can cause them to dry out, shocking the plant. In hotter climates, petunias may need some protection from the late afternoon sun.
  • On the opposite extreme, petunias are not frost-tolerant plants. Plant outside only after the danger of frost has passed, and once the first frost of the season strikes, their growing season has ended.

How To Plant Petunias

When learning how to plant petunias, it’s important to note the differences between buying them from seed or transplanting them. Petunias are very popular annual plants that are prevalent in almost every garden center and nursery. They come in a wide array of varieties, and they transplant very well. You can also start them from seed indoors. The benefit of starting your seeds indoors is that you can seek to grow nontraditional varieties that are not readily available on store shelves.

  • Petunia seeds are tiny and slow to mature, needing 10-12 weeks before flowering begins.
  • Starting petunia seeds indoors 8 to 10 weeks before the last frost date in your area is the best way to grow petunias from seed.
  • Transplant petunia seedlings outdoors once the soil is warm and the threat of frost has passed.
Beautiful bright petunia in the garden near the house.

Where to Plant Petunias

Petunias are popular, not solely for their beauty but also for their versatility in the garden. They add an immediate splash of color no matter where you tuck them in. They are dependable plants that make great accent flowers or can be a fantastic standalone plant. Check out some of our favorite spots to plant petunias:

  • Plant petunias in window boxes, either alone or mixed with other plant varieties.
  • Allow them to spill over the side of containers and raised beds.
  • Densely plant petunias as a vibrant ground cover.
  • Tuck petunias into hanging baskets.
  • Use petunias to fill in spaces between plants in the garden.
  • Interplant petunias with other high-impact container plants.
  • Allow spreading varieties to cascade over a stone wall.
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Petunia Plant Care

Once you’ve learned how to plant petunias, it’s important to learn how to care for them!

How To Water Petunias

Petunias have shallow root systems and enjoy moist soil conditions. Their roots can dry out very quickly.  Therefore, regular watering is paramount to the success of the plant. Make sure that the soil around the plant drains because petunia root systems cannot handle wet feet.  Too much moisture can lead to root rot and the demise of the plant.  Petunias that are planted in containers or hanging planters may require daily watering.

Nutrients Needed For Growing Petunias

Well-fed petunias will reward you with seemingly endless blooms. Keep petunias blooming profusely throughout the summer months by adding a monthly feeding of fertilizer or a slow-release granular type upon planting.  Plants that are confined to containers may require more frequent fertilization than in-ground plants, as the regular watering can wash away lots of soil nutrients.

The Best Ways to Prune Petunias

The degree of pruning that petunia plants need depends on the variety of plants you’re growing, but all plants can benefit from being trimmed up throughout the growing season to counteract leggy plants.

  • All plants will likely benefit from pruning midway through the summer months. This will help all varieties to become fuller and more abundant bloomers. Cut back branches about halfway all around to bring the plants renewed vibrancy.
  • Grandifloras need the most pruning and frequent deadheading so that plants will not become leggy and go to seed.
  • Spreading and wave varieties do not require regular deadheading, although some pinching back of the plant can help shape the plant and produce a fuller plant with more blooms.
Red petunia flowers in a hanging basket.

Common Petunia Pests & Disease

Petunias can be prone to several garden pests and diseases, which can be a nuisance for gardeners. Keep a close eye on your plants for signs of any of these common petunia problems.

  • Aphids
  • Thrips
  • Caterpillars
  • Powdery mildew
  • Root Rot

Recommended Petunia Varieties to Grow

There are four main types of petunia plants which have an array of varieties in each subcategory.  Mix and match some of these extraordinary varieties in your garden beds, pots, and hanging planters.

1.‘Grandiflora’ is the largest petunia variety, producing three to five-inch blooms and attaining heights of ten to twelve inches.

  • ‘Supercascade’
  • ‘Daddy’
  • ‘Dream’

2. ‘Multiflora’ petunia varieties produce medium-sized blooms that range from one to two inches in diameter and grow about eight inches tall.

  • ‘Horizon’
  • ‘Primetime’
  • ‘Celebrity’

3. ‘Spreading or Wave’ petunias can really creep and spread vigorously, spilling out of pots and across garden beds, but only attaining a height of about six inches.

  • ‘Shockwave’
  • ‘Avalanche’

4. ‘Miliflora’ produces small but bountiful blooms that are great in borders and containers.

  • ‘Fantasy’

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