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. 1: 633. Provided by Kentucky Native Plant Society. Scanned by Omnitek Inc. Usage Requirements.
The Plants Database includes the following 4 subspecies of Humulus lupulus . Click below on a thumbnail map or name for subspecies profiles.