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 and dies back in autumn. The plant is dioecious, meaning male and female flowers grow on separate individuals. It is native to Europe, southwestern Asia, and North America and is widely farmed for the brewing industry, as the female cone-shaped flowers—called hops—are used to preserve and flavor beer.

The plant can reach up to 10 meters (33 feet) 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 the longer days of summer, typically in July or August in the Northern Hemisphere. The fragrant flowers are wind-pollinated: male flowers lack petals, while female flowers also lack petals, with the fruit surrounded by bracts and bracteoles instead.

The female flower cones (strobili) are the hops themselves. The fruit is a dry achene that does not split open when ripe; it is surrounded by sepals and bracts and dotted with glands that secrete lupulin. The species is sometimes called a bine rather than a vine because it climbs using stiff, downward-facing hairs that provide grip and stability.

Chemistry

Chemically, H. lupulus contains myrcene, humulene, xanthohumol, myrcenol, linalool, and various tannins and resins. Hops are notable for their secondary metabolites—flavonoids, oils, and polyphenols—that shape the flavor of beer and other hop-infused products. The bitterness comes from acids made of prenylated polyketides, a class of secondary metabolites. Several genes influence taste, 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 contain 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.