Grandiflora petunias generally do not thrive in South Carolina because their large heavy blossoms are prone to damage and rot during hot, humid summers. Grandifloras have large flowers that are often frilled or ruffled along the edges. If you grow most grandiflora petunias, be aware that they will need extra care to look their best. Multiflora petunias are durable and prolific. Their flowers are not as large as the grandiflora types, but they are very free-flowering and vigorous.
Multifloras produce masses of color through summer until frost.
They are resistant to petal blight. Carpet' series petunias are available in many colors. Floribundas are intermediate between the grandiflora and the multiflora groups. Celebrity' series petunias are compact and rain-tolerant. 3-inch flowers in many veined and solid colors.