Evaluation of 125 Petunia Cultivars as Bedding Plants and Establishment of Class Standards

Central Florida has a climate similar to many locations in the southeastern United States and parts of Asia, Europe, and Australia. Thus, Florida is an important testing ground for new bedding plant cultivars not only in the United States, but around the world. The authors evaluated 125 petunia (Petunia ·hybrida) cultivars in replicated class tests at Bradenton, Fla. (lat. 27 4#N, long. 82 5#W) in 2000–04 and at Balm, Fla. (lat. 27 8#N, long. 82 2#W) in 2005–06. In this report they establish petunia classes and cultivar standards for each class, and provide objective plant measurements of vegetative and floral characteristics, and subjective performance ratings. Petunia cultivars were grouped into 73 classes based on the distinguishing characteristics for petunia, which are plant type and height, and flower type, color, and color pattern. Comparisons were made within each class to determine performance and to select a cultivar as the standard for the class—a plant with the highest overall performance rating that can represent the class in future trials against new cultivars. During the initial trials, larger numbers of cultivars were evaluated and eliminated from future comparisons when each class standard was selected. Many flower colors and color combinations, as well as plant types and other distinctive characteristics have been developed for bedding plants. By creating class standards for each distinctive characteristic, better choices over a wider range of classes are available to growers and landscapers in this climate. Cultivars with an outstanding overall performance rating (combined foliage, flower, arthropod feeding symptom, and disease symptom ratings ‡5.5 points on a 1 to 7-point scale) for class standard selections were (floribunda, single mix class) ‘Madness Waterfall Mix’ and [single purple (dark), red-violet class] ‘Madness Magenta’; [grandiflora, single blue (dark) class] ‘Eagle Blue’, (single orange shades/ tints class) ‘Ultra Salmon’, and [single purple (dark), red-violet class] ‘Storm Violet’; and [spreading, normal, orange (dark) shades/tints class] ‘Ramblin’ Salmon Capri’, [orange (light) shades/tints class] ‘Ramblin’ Peach Glo’, [pink (dark) class] ‘Wave Pink’, [purple (dark), blue-violet class] ‘Avalanche Lavender’, [purple (light) blueviolet class] ‘Ramblin’ Lavender’, (red class) ‘Avalanche Red Improved’, (rose class) ‘Avalanche Rose Improved’, (white class) ‘Plush White’, and [spreading, tall; blue (dark) class] ‘Wave Blue’. These cultivars would likely perform well in the southern United States or areas of the world with similar heat and cold hardiness zones. P etunia is considered to be the first cultivated bedding plant. It is the product of complex breeding begun in the 19th century that used two South American species with white (Petunia axillaris) and purple flowers (Petunia integrifolia) (Liberty Bailey Hortorium, 1976). Subsequent petunia breeding resulted in five petunia class divisions: grandiflora, floribunda, milliflora, multiflora, and spreading. In the 1930s, the first consistently double flowers became available from Japan, whereas more flower colors were introduced in Germany from open-pollinated plants. After World War II, breeders began working on larger flowers, better growth habit, and disease and weather resistance. In the 1950s, breeders produced award-winning F1 hybrids, designated as floribundas, by crossing the larger flowered, but heat-sensitive grandifloras with the adverse weather-resistant multifloras (smaller, but more numerous flowers than grandiflora). The hybridization resulted in costly seed, but plants were superior to open-pollinated cultivars. New flower colors, such as true red and the first yellow, and plants with spreading and miniature growth habits (millifloras) expanded the available choices in color and form (Lewis, 1997; Trinklein, 2001). The range of colors, color patterns, and availability of double-flower cultivars is greatest in the grandifloras, floribundas, and multiflora classes. Use of the petunia as a model for plant physiology research resulted in important changes in plant breeding through the understanding of pollen sterility, resulting in economical production of F1 seed. These changes resulted in significant contributions to the further development of the bedding plant industry in the last half of the 20th century (Craig, 2003). In 2005, the wholesale value of petunias was $94 million, and ranked third in value behind pansy (Viola ·wittrockiana)/viola (V. cornuta)