Euthamia Nutt.
Euthamia is a small genus of five species, all native to North America. It was traditionally placed in Solidago but molecular as well as morphological characteristics support its segregation (Haines 2006). Species of Euthamia have gland-dotted leaves, a corymbose (flat-topped) inflorescence, sessile heads and ligular florets are more numerous than tubular florets.
Two closely related species are sometimes cultivated for ornament in Europe: Euthamia caroliniana (L.) E. Greene (syn.: Solidago microcephala (E. Greene) Bush, S. tenuifolia Pursh) and E. graminifolia (Yeo l.c.).
Literature
Haines A. (2006) Euthamia. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 20. Oxford University Press, New York-Oxford: 97-100.
Semple J.C., Ringius G.S. & Zhang J.J. (1999) The Goldenrods of Ontario: Solidago L. and Euthamia Nutt. (3rd ed.). Univ. Waterloo Biol. Ser. 39: VI + 90 p.
Sieren D.J. (1981) The taxonomy of the genus Euthamia. Rhodora 83: 551-579.
Yeo P.F. (2000) Solidago. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 566-570.