Three different definitions of the rosids were used. Some authors included the orders Saxifragales and Vitales in the rosids. Others excluded both of these orders. The circumscription used in this article is that of the APG IV classification, which includes Vitales, but excludes Saxifragales.
The rosids consist of two groups: the order Vitales and the eurosids (true rosids).
The eurosids, in turn, are divided into two groups: fabids (Fabidae, eurosids I) and malvids (Malvidae, eurosids II).
The rosids consist of 17 orders. In addition to Vitales, there are 8 orders in fabids and 8 orders in malvids. Some of the orders have only recently been recognized. These are Vitales, Zygophyllales, Crossosomatales, Picramniales, and Huerteales.
The nitrogen-fixing clade contains a high number of actinorhizal plants (which have root nodules containing nitrogen fixing bacteria, helping the plant grow in poor soils). Not all plants in this clade are actinorhizal, however.
^Chalk, L. (1983), "Wood structure", in Metcalfe, C.R.; Chalk, L. (eds.), Wood Structure and Conclusion of the General Introduction, Anatomy of the Dicotyledons, II (2nd ed.), Clarendon Press, pp. 1-51 [1-2 by C. R. Melcalfe], ISBN978-0-19-854559-0
^Hutchinson, John (1979) , The Families of Flowering Plants (3rd ed.), Oxford University Press, ISBN9783874291606
^Worberg, Andreas; Alford, Mac H.; Quandt, Dietmar; Borsch, Thomas (2009), "Huerteales sister to Brassicales plus Malvales, and newly circumscribed to include Dipentodon, Gerrardina, Huertea, Perrottetia, and Tapiscia", Taxon, 58 (2): 468-478, doi:10.1002/tax.582012