Evaluation of Seven Complex Pennisetum Hybrids for Container and Landscape Performance in the Pacific Northwestern United States

Abstract

Ornamental grasses such as fountaingrass or napiergrass, collectively called pennisetums, belong to the genus Pennisetum, which is a diverse genus with over 80 species adapted to a wide range of climatic regions and known for its drought tolerance. Breeding efforts have led to improvements such as more intense purple foliage color, disease resistance, and apparent sterility. These improved forms have been developed and tested in the eastern United States. The objective of this research was to evaluate container and field performance of seven new complex hybrid pennisetums in the Pacific northwestern United States. Two completely randomized experiments with three replications were conducted over 2 years (2010 and 2011) at two locations. We selected seven trispecific hybrid pennisetums resulting from interploid and interspecific crossing that were given accessions Tift 5, Tift 6, Tift 10, Tift 11, Tift, 13, Tift 15, and Tift 26. Experiment 1 evaluated container performance in Corvallis, OR, while Expt. 2 evaluated field performance in Aurora, OR. Size index (SI), growth form rating, and color rating were collected and analyzed separately by location. In the container study, significant differences were observed among selections for growth form in 2010 and color ratings in both 2010 and 2011. In 2010, Tift 6, Tift 11, Tift 13, and Tift 15 had the highest growth form rating. For color rating, Tift 5, Tift 10, and Tift 26 were among the four highest rated selections in both years. In the field study, Tift 5, Tift 10, Tift 11, and Tift 26 had the highest SI when data were pooled over the 2 years, but all selections reached acceptable size for landscape use during both years of the study. Similarly, there were color differences among selections with Tift 5, Tift 10, Tift 15, and Tift 26 being highest rated. None of the selections survived below winter temperatures of −5 °C at either location during either year of the study. Our evaluations indicate that these selections have potential in the Pacific northwestern United States as annuals. Differences in complex hybrid pennisetums were observed in SI, growth form rating, and color rating. These differences demonstrated the variation among selections and will allow producers to choose desired traits based on market preference.