The hop plant is a creeping perennial with several stems or branches attaining a length of fifteen to twenty-five feet. It has numerous, opposite three to five lobed, palmately veined, coarsely toothed leaves with long leaf stalks (petioles). Flowers unisexual, that is staminate and pistillate flowers separate, either on separate plants (dioecious) or upon different branches of the same plant (monoecious). Flowers insignificant in loose, drooping axillary particles. Fruit a cone-like catkin usually designated a strobile.

The hop has been., called the northern vine. It is found in a wild state throughout Europe, excepting the extreme north, and extends east to the Caucasus and through central Asia. It is a handsome plant and not infrequently used as an arbor plant. The lower or basal leaves are very large, gradually decreasing in size toward the apex. H. lupulus, is the only representative of the genus.

It is rather remarkable that a plant so widely distributed and familiar should not have been known to the Greeks and Romans. Its cultivation in Europe dates back to the eighth and ninth centuries. It was, however, not extensively cultivated until about the sixteenth and seventeenth centuries.

The word hop (German, Hopfen) is of very uncertain origin. According to some authorities it is traceable to the old English, hoppan, in reference to the habit of the plant in climbing over hedges and fences. Humulus is said to refer to its habit of creeping over the soil. Lupulus (diminutive of lupus, wolf) is said to refer to the pernicious and destructive influence the hop plant has upon plants which it uses as a support, especially the willows. Plinius named it Lupus salictarius, that is, the willow wolf or willow destroyer.

Beside the countries above named hops is also cultivated in Brazil and other South American countries, Australia and India. There are several cultivated varieties. According to most authorities it is not supposed to be indigenous to North America, but Millspaugh expresses it as his opinion that it is indigenous northward and westward, growing in alluvial soil, blossoming in July and fruiting in September.

The plants are planted in rows and the rapidly growing branches trained upon poles stuck into the soil. Three or four male plants (with staminate flowers) are grown in an acre patch to supply the necessary pollen. Some authorities state, however, that the female plants develop enough staminate flowers to effect pollination. It is extensively cultivated in England, Germany and France. Also in New England, New York, Michigan, and in fact nearly every State in the Union.

In Belgium the young, tender tops of the plants are cut off in the spring and eaten like asparagus, especially recommended to the pale and anaemic and those with scrofulous taints.

The peculiar hop-like fruiting known as strobiles, are collected in the fall of the year (September to October), dried and tightly packed into bales. The base of the scales, of the strobile are covered with a yellowish powder, consisting of resin bearing glands, known as lupulin. One pound of hops yields about one ounce of lupulin. Since the medicinal virtues of hops reside in the lupulin it will be readily understood that the hops from which the glands have been removed is of little or no medicinal value. Lupulin as well as the hops have a faint, peculiar, somewhat yeasty odor, which increases with age due to the development of valerianic acid. For medicinal purposes only fresh hops should be used.