Information on Petunia Plants

Petunias are part of the Solanaceae family.

Petunias are popular annual flowering plants native to South America. They are attractive, easy to grow and bloom throughout the summer months. Petunias are available in almost any color and have a sweet, pleasing smell. They work well in hanging baskets or as ground cover plants depending on the variety; they also make showy additions to window boxes, in flower beds or as colorful borders.

Milliflora and Ground Cover Petunias

Millifloras are some of the smallest types of petunias. Their blossoms grow around 1 to 1.5 inches in diameter. They are available in several different cultivars including the Fantasy Series, a mounding variety that reaches heights of 10 inches. Spreading or ground cover petunias are another small-blossomed variety. These plants have a rapid growth rate and can quickly cover walls, gardens or hillsides in an abundant layer of blossoms. They work particularly well in hanging baskets, since the entire length of the stem produces flowers.

Multiflora and Grandiflora Petunias

Multiflora petunia plants have a compact form and produce large numbers of double and single varieties of blossoms. Several multiflora cultivars include Primetime, which produces 2.25-inch blossoms, and Carpet, which yields 1.5- to 2-inch flowers. Grandiflora plants are the largest type of petunia, growing up to 15 inches tall. Most grandifloras have an upright, mounding form, while others have trailing forms that complement hanging baskets. The plants yield 3- to 4-inch single or double blossoms, and some varieties have fringed or ruffly petals.

Petunia Care

Petunias need between five and six hours of full sunlight each day to remain healthy. They bloom more vigorously if they receive all-day sunlight. They prefer well-drained, nutrient-rich soil and benefit from an application of a balanced fertilizer about once every three weeks depending on the variety. Container petunias need to be watered several times a week, but outdoor petunias usually only need a thorough watering about once every seven to 10 days. Pinching back multifloras and grandifloras encourages them to branch.

Pests and Problems

Phytophthora, pythium, rhizoctonia and thielaviopsis fungi cause root rot in petunias. The roots become discolored and water-soaked; the plants appear wilted or discolored. The Botrytis cinerea fungus causes gray mold or botrytis blight. Brown spots form on the leaves, stems and blossoms, and a gray fungus grows in the dying plant tissue. Viruses such as the cucumber mosaic virus cause streaking, spotting and stunted growth on the foliage. Leaf miners, cutworms, caterpillars and aphids feed on petunia foliage.

References

• Fine Gardening: Genus Petunia
• Clemson Cooperative Extension; Petunia; Karen Russ; September 2007
• University of Minnesota Extension; Growing Petunias; Deborah Brown; 2009
• Iowa State University: Growing Petunias
• University of Rhode Island Landscape Horticulture Program; Petunias; Dale T. Lindgren; 2000
• Cornell University: Botrytis Blight

Resources

• Kansas State University; Diseases of Flowering Potted Plants; Ned Tisserat