Solidago gigantea subsp. serotina (4810' N 1629' E)

Description:

2008.08.05: Austria, Vienna XXII. district, 155 m AMSL, fallow land (Lobau national park).Flowering from july/august till october.Very common, invasive (native of North America).German name: Riesen-Goldrute.ID: Fischer, Exkursionsflora 3rd; oftentimes mistaken for Solidago canadensis (I made the same error myself): the latter has a hairy stem while the former hasn't, or has at most some hair on its inflorescence (which usually is the case for populations in Lobau). Instead, the stem of S. gigantea has a 'floured' look, and you can wipe it off, as is shown here.