How to Grow Petunias

Petunias are a great choice for a brightly colored garden. They are annual flowering plants, native to Argentina, and bloom from spring until frost. The petunia family includes great variety: single and double blooms, ruffled or smooth petals, striped, veined or solid colors, mounding and cascading habits and even some fragrance. Most of the petunias sold today are hybrids, developed for specific design purposes.

Among the several varieties of petunias, you will find grandifloras and multifloras, the two oldest types of these flowering annuals. Both are somewhat mounding. Grandiflora has larger flowers, but Multiflora holds up better in the rain.

Spreading type petunias, which include The ‘Wave’, ‘Supertunia’, ‘Cascadia’ and ‘Surfinia’ series are some of the most popular petunias because most don’t need deadheading and they can be used as bedding plants, ground covers or trailing in containers.(Source: About.com.gardening)

Site and Soil

There is one essential thing petunias require to grow beautifully: it is a location with plenty of light. They need at least five or six hours of good sunlight; they'll perform even better when located in full sun all day. They will produce more flowers if they get more light. In case you have shady places, your choice should fall on impatiens, which bloom better there.

Since petunias  grow in moist ground, you will want to keep them well watered. Petunias don't require terribly rich soil, but it must be one that drains decently. "It's always useful to improve garden soil by conditioning it with organic matter, such as baled peat moss, well-rotted leaf compost or manure"(Deborah Brown, Minnesota University http://www.extension.umn.edu/distribution/horticulture/dg1120.html).

Spread the organic matter two to three inches thick. Then incorporate it into the soil to a depth of eight to ten inches, using a rototiller or garden fork. This helps open up heavy clay soil, which improves drainage, but can also increase the ability of light, sandy soil to hold moisture and nutrients.

Planting Tips

The following tips were taken from "Growing Petunias", by Deborah Brown, University of Minnesota. She recommends:

"Wait until soil warms to about 60 degrees and frost danger has passed before transplanting petunias into the garden. Space grandifloras and multifloras about twelve inches apart in full sunlight, or several inches closer together when planted in a shadier location. Milliflora petunias can be spaced as close as four to six inches, but the spreading ground-cover types of petunias should be planted at least one and a half feet apart. Petunias must be planted much more closely together in containers in order to look attractively full right from the start.

Plan to provide some protection from midday sun for the first few days, if weather is hot or windy with few clouds at transplanting time. When grandifloras or multifloras grow about six inches tall, pinch them back to encourage rapid formation of flowering side shoots. Do not pinch millifloras or "spreading" petunias.

Whenever feasible, it's a good idea to remove faded flowers, including the portion below each flower where seeds will develop. This practice, called "deadheading," encourages blooming by preventing seed maturation. Although it may not be practical to deadhead masses of petunias in the garden, it's a must for flowering annuals in containers. Deadheading not only helps prolong blooming, it also keeps plants looking fresh, healthy and well-groomed."

Hopefully, you will enjoy the sight of your brilliant petunias as they bloom in your garden throughout summer.