Solidago gigantea, Aiton

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1976, Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae), Cambridge University Press : 110

4. S. gigantea Aiton , Hort. Kew. 3: 211 (1789).

Like 3 but stems 50-250 cm, glabrous, often glaucous except in the inflorescence; leaves usually glabrous; involucre usually 3-5-5 mm. 2n = 36. Naturalized from gardens throughout much of Europe. [Au Az Be Br Bu Cz Da Ga Ge Hb He Ho Hs Hu It Ju Po Rm Rs (W) Su.] (North America.)

The naturalized plants in Europe are mostly referable to subsp. serotina (O. Kuntze) McNeill , Bot. Jour. Linn. Soc. 67: 280 (1973), which is said always to be tetraploid, but the diploid subsp. gigantea , with the leaves pubescent on the veins beneath, the involucre 3-2-4 mm, and the achenes usually glabrous, may also occur.