Giant Hyssop

Retrieved from: http://www.finegardening.com/plantguide/agastache-foeniculum-golden-jubilee-anise-hyssop.aspx

Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 3: 112.

Retrieved from: http://www.minnesotawildflowers.info/flower/blue-giant-hyssop