2018 ASHS Annual Conference

Zinnia peruviana L. is a flowering annual native to Central America. An interesting characteristic about this species is that it is the only member of the genus Zinnia that is self-compatible except for a popular cultivated Zinnia known as Zinnia tenuifolia ‘Red Spider’. Curiously, there is no published literature of the discovery of Zinnia tenuifolia even though it is listed as a species in seed catalogs. Zinnia peruviana was first introduced into cultivation by Phillip Miller, who brought seeds back to England in 1753. It was subsequently described as Chrysogonum peruvianum by Carl Linnaeus. Linnaeus later changed the name to Zinnia pauciflora L., but this name has since been reduced to a synonym of Zinnia peruviana. In 1755, the director of the botanical garden in Vienna, Nikolaus Joseph von Jacquin, was commissioned by Francis I of Austria to undertake a plant expedition to Central America. He returned in 1759, with a number of plant species, including seeds of a wild Zinnia species that he described as Zinnia tenuiflora Jacq. This name was later reduced to synonymy beneath Zinnia peruviana. Today, many seed companies employ various scientific names for Zinnia ‘Red Spider’, including Zinnia tenuiflora, Zinnia tenuifolia, and Zinnia peruviana syn. tenuifolia, but the most common name used in seed catalogs is Zinnia tenuifolia ‘Red Spider’. Considering the lack of a published protologue, the most likely origin of this name is a repeated industry typo of Zinnia tenuiflora, where ‘flora’ was changed to ‘folia’ to produce Zinnia tenuifolia. To test this hypothesis, we compared accessions of Zinnia peruviana obtained from the USDA Ornamental Plant Germplasm Center to commercially obtained seed of Zinnia tenuifolia ‘Red Spider’ for leaf dimensions, floret size and color, plant height, and internode length. ‘Red Spider’ had similar plant and flower morphology to the Z. peruviana accessions, and all were self-fertile. A cDNA analysis also revealed a great degree of similarity between Zinnia peruviana and Zinnia tenuifolia ‘Red Spider’. Based on these results, Zinnia tenuifolia ‘Red Spider’ should be considered a selection of Z. peruviana and not a distinct species.