Petunias: Rediscover These Amazing Annuals

Are petunias perennials or annuals?

Although they are actually classified as tender perennials, they won't tolerate frost so they are commonly grown as annuals in most climates.

Sun or shade?

Full sun

Bloom time:

Summer

Color and characteristics:

You can find them in just about any color, even black, as well as striped, veined, and speckled patterns. The variety of flower forms is also impressive, ranging from petite to palm-sized in single or double blooms with ruffled, fringed, or smooth edges.

Nearly all petunia plants sold today are hybrids. Some new petunia varieties and hybrids have become so popular, they have created a class of their own, such as the Supertunia® and Wave® series of plants.

Supertunias®:From Proven Winners®, vigorous bloomers that produce flowers in a broad range of colors.

• Supertunia® Vista: Landscape plants with medium-sized flowers, growing up to 2 feet tall and 3 to 5 feet wide.
• Supertunia® Charm: Densely-branched container plants with small flowers.
• Supertunia® Trailing: Strongly trailing plants with medium flowers.
• Supertunia® Double: Plants bloom with fully doubled flowers.

Spreading, or Wave® petunias: Introduced by Ball Seed Co., energetic growers with trailing stems that spread up to 4 feet or more.

Grandifloras: One of the oldest types, producing large, although fewer, flowers; mounding to 15 inches.

Multifloras: Blooms with smaller flowers and has a more compact growth habit.

Floribundas: Hybrids of grandiflora and multiflora, producing grandiflora-like blooms with the vigor of a multiflora.

Millifloras: Only about 8 inches tall and wide and produce tiny 1-inch blooms.

When to plant:

In spring, after the threat of frost has passed.

Where to plant:

For the best performance, plant in full sun (at least six hours a day). They will tolerate some shade, but may not flower as prolifically.

Soil:

They grow best in a light, fertile soil that provides good drainage and is slightly acidic (pH 6 to 6.5). In heavy clay soils, work some compost, or other organic matter into the ground before planting. When planting in containers, use a free-draining soilless potting mix fortified with a slow-release fertilizer.

Grow petunias from seed:

You can also grow many types from seed if you’re after a certain variety not available as a transplant. Because petunia seeds are very tiny and slow to germinate, you’ll have better success starting the seeds indoors 8 to 10 weeks before the last frost date in your area and transplanting the seedlings into the garden once the soil warms up.

Water:

Like many sun-loving flowering annuals, petunias need regular watering because their shallow root systems dry out quickly. However, make sure the soil is well drained because soggy soil can cause root rot and yellowed foliage. Petunias grown in containers may need more frequent watering, possibly every day, especially in hot weather.

Fertilizing:

Petunias need a lot of refueling throughout the summer to keep them blooming vigorously. Apply a monthly dose of liquid fertilizer or a slow-release granular fertilizer at the time of planting. Plants grown in containers often need more frequent fertilizing because the increased watering washes nutrients out of the soil.

Pruning and deadheading:

The amount of pruning required often depends on the variety you’re growing.

• Traditional grandifloras require the most work and need frequent deadheading to prevent plants from going to seed.
• Newer self-cleaning and spreading varieties will do fine without pinching or pruning, but occasional deadheading will boost flower production and create fuller plants.
• If your plants begin to get leggy and bloom less heavily, shearing them back will encourage new growth and more branching.

Pests and diseases:

Petunias can be bothered by pests like thrips, mites, caterpillars and budworms; as well as powdery mildew and various types of rot.

• Mites and thrips can be treated with applications of neem oil or insecticidal soap.
• Caterpillars or budworms can be hand picked and dropped in a bucket of soapy water, or treated with a Bacillus thuringiensis (Bt) spray, but don't apply when butterfly caterpillars may be present. Watch this video to learn more about how to get rid of budworms.
• Root, stem, or crown rot can be caused by poor drainage or overwatering.
• Powdery mildew can be caused by overcrowding as well as wet conditions.

Get more advice on keeping your petunias blooming all summer long:

Petunias are very popular flowers for adding instant color to a garden. They are incredibly versatile and can be used in many ways. Here are some ideas:

• Plant them as colorful additions to seasonal landscape beds
• Grow them individually in hanging baskets or along with other strong growers
• Use them in containers as the filler or spiller component
• Plant petunias in masses for a dramatic blanket of color
• Cover bare spots in your garden quickly and prevent weeds
• Fill your window boxes with petunias that complement your home’s color scheme
• Try them in hayracks along a sturdy fence or in a DIY copper wire plant hanger