to italicize or not to italicize...
David Ehrlich (Mon, 15 Sep 2008 08:58:51 PDT)

My bible on Plant Systematics gives the ICBN recommendations, which are that both the generic and specific epithets should be italicized.  The authority is not italicized.  If you are referring to a variety or subspecies, the “var.” or “subsp.” is not italicized, but the following epithet is, e.g.,
Lyonia ligustrina (L.) DC. var. filiosiflora (Michx.) Furlow

Higher taxa are always capitalized; they are generally italicized by Europeans, but not by Americans.

Cultivar names should have a capital initial and either be included in single quotes or preceded by “cv.”  They are never italicized.

Hybrid names are preceded by ´, and are italicized.

David Ehrlich