Populus tremula; Aspen is a rare tree species, only to be found in the wild in some localities in eastern Iceland and in only a very few localities in northern Iceland. It doesn't flower on Iceland, so it spreads only by its rootstocks. I found this species in the forests of Hallormstaðir near Egillsstaðir (eastern Iceland). On Iceland it grows up to 6 meter but remains very short where sheep can graze. The leaf shape (see photo) is unique.
Apart from the indigenous Aspen another poplar has been introduced and grows (planted) commonly in more or less urban areas being Populus trichocarpa (Black Cottonwood). It has large (8-18 x 5-12 cm's) leaves with smooth edges.
Both are a members of the willow family (Salicaceae). The Icelandic name of this species is Blæösp.