Humulus lupulus

Humulus lupulus, the common hop, is a flowering perennial in the Cannabaceae family—the same group as hemp and marijuana. It is a herbaceous climber that emerges anew each spring from a cold-hardy rhizome, then dies back in autumn. The plant is dioecious, meaning male and female flowers grow on separate individuals, and it is native to West Asia and Europe, though it has been introduced and naturalized in North America. Its female cone-shaped flowers, called hops, are widely farmed for the brewing industry, where they preserve and flavor beer.

The plant can reach up to 10 meters tall and live for about 20 years. Its leaves are simple, with three to five deep lobes, and may be arranged opposite or alternate along the stem. Flowering is triggered by longer summer days, typically occurring in July or August in the Northern Hemisphere. The fragrant flowers are wind-pollinated: male flowers lack petals, while female flowers also lack petals; the cone is composed of bracts and bracteoles, not petals.

The female cones (strobili) are the hops. The fruit is a dry, non-splitting achene, surrounded by bracts and dotted with glands that secrete lupulin. Because the plant climbs using stiff, downward-facing hairs for stability, it is sometimes called a bine rather than a vine.

Chemistry

Chemically, H. lupulus contains myrcene, humulene, xanthohumol, myrcenol, linalool, and various tannins and resins. Hops are unique for their secondary metabolites—flavonoids, oils, and polyphenols—that shape the flavor of beer and other hop-infused products. The bitter taste comes from acids made of prenylated polyketides, a group of secondary metabolites. Several genes influence this bitterness, including O-methyltransferase 1, geranyl diphosphate synthase, and chalcone synthase.

Genomic studies show that thousands of years of human selection have enhanced aroma, bitterness, and yield in cultivated varieties. The plant’s growth, flowering, and stress responses are linked to homologous primary contigs—overlapping DNA sequences inherited from a common ancestor—that show high sequence variation. Genes with higher divergence rates in these regions are tied to flowering, growth, and responses to both abiotic and biotic stress. These stress responses help explain differences in cultivation difficulty among geographically distinct hop varieties.