2018 ASHS Annual Conference

North American shrubs in the genus Ptelea have untapped potential to add diversity to landscapes and to support populations of pollinators and swallowtail butterflies. Like other members of the Rutaceae, Ptelea trifoliata and Ptelea crenulata are notably aromatic, but intriguingly different descriptions of their floral fragrance led us to use gas chromatography and mass spectrometry to separate and identify the volatile chemicals emitted by flowers of these species. Chemicals identified include nonanal, 1- and 2-hexanol, benzyl acetate, limonene, linalool, bergamotene, bisabolol, bourbonene, farnescene, myrcene, and trans-ocimene. While these results are consistent with analyses of aromatics from flowers of other members of the Rutaceae, the status of Ptelea as dioecious species led us to question whether aromatic profiles of staminate and pistillate flowers differ. While similar compounds are present in both floral types, concentrations are different in ways that appear to affect how people perceive the fragrance. Human-subject assessments of floral volatiles of Ptelea confirm that pistillate flowers are considered to smell floral and citrusy, whereas pungent odors with vegetative undertones were additional scents that emanated from staminate flowers. This work helps to resolve conflicting reports of the floral fragrance of Ptelea, which range from hyacinth-like to skunk-like. Chromatography, spectrometry, and human responses indicate that the floral fragrance of Ptelea combines citrusy, spicy, floral, and pungently vegetative scents.