Aaron's rod vs mullein

Aaron's rod

noun
  • Goldenrod, the Solidago genus of North American plants with yellow flowers. 

  • Hylotelephium telephium (syn. Sedum telephium; orpine, livelong, or live-forever). 

  • A rod-shaped molding decorated with an entwined snake, and sometimes leaves, vines, and/or scrolls. 

  • Verbascum thapsus, the great mullein, common mullein, or hag-taper. 

mullein

noun
  • Any of a few hundred species of European and Asian plants, of the genus Verbascum, especially that majority that have yellow flowers. Some species have been introduced to other continents, where some are now seen as invasive pests. Some species, though far from all, have downy leaves, hence common names such as: "velvet plant". 

How often have the words Aaron's rod and mullein occurred in a corpus of books? (source: Google Ngram Viewer )