Pollen traits of some American ashes investigated by a scanning electron microscope

Over last 130 years the American assh was often used for afforestation of Croatian lowland areas where the native narrow leafed ash (Fraxinus angustifolia Vahl) did not grow well. Due to unequivocal species identification of the American ash F. americana L. or F. pennsylvanica Marshall, pollen samples of concerned specimens were collected. Based on species pollen samples of F. americana and F. pennsylvanica, collected from trees growing at the Royal Botanical Gardens Hamilton in Canada, and on their distinctive morphological features, pollen samples of American ash trees from a plantation Črnovščak in Dugo Selo near Zagreb and from arboricultures in Zagreb were determined as Fraxinus pennsylvanica.