Hop Botany and Physiology

Hop (Humulus lupulus L.) is a dioecious perennial plant with climbing habitus, belonging to the Cannabaceae family. The genus Humulus is native of Asia and has spread to North America and Europe, consisting of three species: Humulus lupulus L., H. yunnanensis Hu. and H. japonicus Siebold & Zucc. The main species cultivated all over the world is H. lupulus L., usually known as hops. The cultivation of hop is due to the valuable intrinsic characteristics of the female inflorescences, botanically known as “strobiles” or commonly called “hop cones”. The hop cones are used mainly in the brewing sector, but the plant as a whole is gaining importance for the presence of valuable bioactive compounds. In this chapter, the botany of hop varieties will be discussed, with a particular attention to stems, leaves, flowers and seeds from a morphological, physiological and anatomical point of view. Many of the anatomical features are genetically fixed and characteristic, and we will point out the anatomy of hop tissues.