Iris root, also called orris, is a very expensive fine perfumery ingredient that derives its characteristic elegant scent from aroma molecules called irones. Orris oil is extracted from aged dried roots of Iris pallida plants. Orris has facets of woods, powder, berry, and violet, and it serves as a perfumery fixative. Very pure isolated irones are also available and are very expensive. Sometimes when iris is listed as a note in perfume, it means an accord that makes use of irones but adds other components to emphasize the floral facets.
Iris Pallida bloom shown.