Humulus lupulus L.

Common Hops

© SRTurner

Family - Cannabaceae

Habit - Dioecious perennial forb with stout rhizomes.

Stems - Twining, to 6 m, branched, sparsely to moderately pubescent with 2-armed hairs on the ridges, minutely hairy or glabrous between them, rough and prickly to the touch.

	Stem and node, stipules.
© SRTurner

Leaves - Mostly opposite, petiolate, stipulate. Petioles 1-8 cm long, mostly shorter than the blades, usually sparsely to moderately pubescent with stiff, 2-armed hairs. Blades 3-14 cm long, 2-13 cm wide, narrowly to broadly ovate in outline, unlobed or with 3 shallow to relatively deep lobes, the margins sometimes with short, soft hairs, the upper surface sparsely roughened with stiff, bulbous-based, prickly hairs, the undersurface not roughened, glabrous or more commonly sparsely to moderately pubescent with short, fine hairs, also with yellowish, sessile glands.

	Lobed leaf.
© SRTurner

	Unlobed leaf.
© SRTurner

	Leaf abaxial.
© SRTurner

	Leaf abaxial surface.
© SRTurner

	Leaf petiole.
© SRTurner

	Pressed leaves.
© DETenaglia

Inflorescences - Staminate inflorescences open terminal panicles 3-15 cm long, 2-3 cm wide. Pistillate inflorescences short, dense spikes 0.5-1.5 cm long at flowering, elongating to 1-5 cm long at fruiting, the bracts 10-18 mm long, ovate to elliptic-ovate, the margins glabrous, the outer surface glabrous or sparsely to moderately hairy, also with yellowish to orangish, stalked glands, especially near the base.

	Pistillate inflorescence.
© DETenaglia

Flowers - Sepals 1.5-2.5 mm long, lanceolate to ovate or oblong-ovate, glabrous or hairy, also with yellowish to orangish, stalked glands. Staminate flowers 1.5-3.0 mm long. Stamens with the anthers usually having orangish glands.

	Pistillate flowers.
© DETenaglia

Fruits - Broadly ovoid, sometimes slightly flattened, enveloped by the persistent enlarged bracts and membranous calyx, 2.0-2.7 mm long, 2.0-2.5 mm wide, the surface smooth, yellowish brown, the persistent calyx occasionally darker-mottled.

	Infructescences or "cones."
© SRTurner

	Single "cone" infructescence.
© SRTurner

Flowering - July - October.

Habitat - Streambanks, pond margins, bottomland forests, and moist ledges of bluffs, fencerows, railroads, roadsides, disturbed areas. Also cultivated.

Origin - Dependent upon variety. Native to the U.S., Canada, Asia, and Europe.

Lookalikes - H. japonicus, but the plant is unmistakable when in fruit.

Other info. - This species can be found throughout much of Missouri, but not particularly common anywhere in the state, and uncommon or absent in the Ozark and Bootheel regions. It is widespread across the continental U.S. and Canada, though its distribution defies description and has surely been influenced by widespread cultivation. The plant is easily recognized when in fruit by its distinctive clusters of persistent bracts, which hide the actual fruits. The leaves can be lobed or unlobed, with petioles that are usually scabrous and somewhat "clingy" to the touch.

The distinctive infructescences of this species, termed "cones" in the brewing industry, are the hops used in brewing beer and ale. The plants, of which there are numerous cultivars bred for flavor characteristics, are cultivated on tall scaffolds, upon which they climb with the aid of the 2-armed hairs on their stems and petioles. Typically, the scaffold is hinged near the base and can be tipped down for harvest. The cones contain yellowish glands which exude a resinous gum called "lupulin," and numerous methods have been invented to extract and concentrate the glands or the lupulin itself. The active principles of lupulin are terpenoid acids and hydrocarbons and flavonoids. These impart a prized flavor and bitterness to beer, and also act as a preservative.

In Missori, three varieties of the species are recognized, and are distinguished by leaf lobing and density of hairs and glands on the leaf undersurface. Another species, H. japonicus Sieb. & Zucc., is very similar but has 5-lobed leaves. This species, also known as Japanese hops, is considered a noxious and invasive pest, often growing rampantly on riverbanks and overwhelming other vegetation. The hairs on its stems and petioles are stiff and sharp enough to draw blood on bare legs of anyone careless enough to walk through a patch of the plants. It has no value in brewing.

Photographs taken at Lincoln Boyhood Memorial Park, IN., 8-4-06 (DETenaglia); also near St. Albans, Franklin County, MO, 10-15-2011, along Fox Creek, St. Louis County, MO, 9-2-2020, and along the Katy Trail near Marthasville, Warren County, MO, 9-15-2024 (SRTurner).