Source: Magness et al. 1971
The hop plant is a strong-growing vine which rises each year from a perennial crown. The top dies at the end of the season. Vines attain growth of 20 or more feet and bear numerous side branches and large, rough 3-pointed leaves. The valuable part of the plant is the fruiting bodies, which resemble pine cones but consist of leafy bracts on a central stem. These cones are borne in clusters, mainly on side branches and are generally 2 to 4 inches long and an inch or more in diameter. They have a characteristic aroma and bitter taste due to essential oils and resins. They are used to give characteristic flavors to beer and other alcoholic malt beverages.
In commercial production hops are trained on high trellises. Fruiting bodies begin to form in midsummer and are mature for harvest about two months later. In harvesting, vines are mainly cut and passed through machines that comb off the cones and largely separate them from leaves and other debris. Cones are then dried in kilns to a moisture content of about 10 percent, after which they are pressed into bales or extracted for flavoring.
In beer manufacture about a pound of hops is added to from 30 to 50 gallons of the malt-water mixture prior to fermentation. After boiling and cooking, yeast is added for fermentation. Finally the hops and precipitated proteins are removed prior to bottling or putting in kegs.
Hops are grown on about 30,000 acres in the United States, almost all in Washington, Oregon, Idaho and California. Production of dried hops averaged 23,730 tons for 1966 and 1967.