Hop (plant)

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Common Hop plant
Scientific classification

Humulus lupulus L.
Humulus japonicus Siebold & Zucc.
Humulus yunnanensis Hu

The hop (Humulus) is a small genus of flowering plants, native to the temperate Northern Hemisphere. The female flowers, commonly called hops, are used as flavouring and stabilisers during beer brewing.

Although frequently referred to as the hop vine, it is technically a bine; unlike vines, which use tendrils, suckers, and other appendages for attaching themselves, bines have stout stems with stiff hairs to aid in climbing. It is a perennial herbaceous plant which sends up new shoots in early spring and dies back to the cold-hardy rhizome in autumn. Hop shoots grow very rapidly and at the peak of growth can grow 20-50 cm per week. Hop bines climb by wrapping clockwise around anything within reach, and individual bines typically grow between 2 to 15 m depending on what is available to grow on. The leaves are opposite, with a 7-12 cm petiole and a cordate-based, palmately lobed blade 12-25 cm long and broad; the edges are coarsely toothed. When the hop bines run out of material to climb, horizontal shoots sprout between the leaves of the main stem to form a network of stems wound round each other.



There are three species, one with five varieties:

  • Humulus japonicus (syn. H. scandens). Asian Hop. Leaves with 5-7 lobes. Eastern Asia.
  • Humulus lupulus. Common Hop. Leaves with 3-5 lobes. Europe, western Asia, North America.
    • Humulus lupulus var. lupulus. Europe, western Asia.
    • Humulus lupulus var. cordifolius. Eastern Asia.
    • Humulus lupulus var. lupuloides (syn. H. americanus). Eastern North America.
    • Humulus lupulus var. neomexicanus. Western North America.
    • Humulus lupulus var. pubescens. Midwest North America.
  • Humulus yunnanensis. Yunnan Hop. Leaves with 3-5 lobes, densely hairy below. Southeast Asia (endemic in Yunnan, China).



The first documented instance of hop cultivation was in 736, in the Hallertau region of present-day Germany, although the first mention of the use of hops in brewing was in 1079. Hops were introduced to British beers in the early 1500s, and hop cultivation began in the United States in 1629.

Today, the principal production centres for the UK are in Kent (which produces Kent Golding hops) and Worcestershire, and Washington state for the USA; other important production areas include Belgium and Germany.

Propagation and pests

The European Hop is propagated either by nursery plants or by cuttings. These are set in "hills", formed by digging holes in the spring, which are filled with fine leaf mould. The density of the holes varies from 3-5 holes per m². One, two, or three plants are put in each hill; although, if hops are designed to be raised from cuttings, four or five of these, ranging from 7 to 10 cm (3-4 inches) in length, are planted 3-5 cm deep in fine leaf mould.

Hop growing, though profitable when it succeeds, is risky, with several significant insect pests causing damage, including the European Corn Borer Ostrinia nubilalis and the Hop froghopper Aphrophora interrupta. Hop gardens on chalky soils are particularly subject to damage. In June and July, the hops are liable to be damaged by an aphid, Myzus humuli. This insect, however, does not endanger the growth of the plant, unless it is already in a weak state from root damage by the larvae of the ottermoth, Phalaena humuli. The roots are also attacked by the larvae of the Ghost Moth, Hepialus humuli. The foliage is sometimes eaten by the larva of another moth, the Currant Pug.


At the end of the first year it becomes necessary to put poles into the hills, around which the bines reared from plants are wound; at the expiration of the second year, full-sized poles, from 5-6 m long, are set (though the hop bines will run to the height of 15 m) in the proportion of two poles to each hill, and a similar number of hop-plants are fastened loosely round each pole, by means of withered rushes. Hops begin to flower about the latter end of June or the beginning of July. The poles are now entirely covered with foliage, and the pendent flowers appear in clusters. The hops, which are the scaly seed-vessels of the female plants, are, when the seed is formed around the end of August, picked off by hand; for this purpose the poles are often taken down with the plants clinging to them. The seeds are then dried, exposed to the air for a few days, and packed in sacks and sent to market.



Hop acids have a mild antibiotic effect against Gram-positive bacteria, and favours the exclusive activity of brewing yeast in the fermentation of beer. The flavour imparted by hops varies greatly by variety and use: hops boiled with the beer (known as "bittering hops") produce bitterness, while hops added to beer later impart some degree of "hop flavour" (if during the final 10 minutes of boil) or "hop aroma" (if during the final 3 minutes, or less, of boil) and a lesser degree of bitterness. Adding hops after the boil, a process known as "dry hopping", adds very little bitterness. The degree of bitterness imparted by hops depends on the degree to which otherwise insoluble alpha acids (AAs) are isomerized during the boil, and the impact of a given amount of hops is specified in International Bitterness Units. Unboiled hops are only mildly bitter.

"Noble hops" are low in bitterness and high in aroma, and traditionally consist of four central European cultivars, 'Hallertauer Mittelfrueh', 'Tettnanger', 'Spalter', and 'Saaz'.

They contain high amounts of the hop oil humulene and low amounts of alpha acids cohumulone and adhumulone, as well as lower amounts of the harsher-tasting beta acids lupulone, colupulone, and adlupulone. Humulene imparts an elegant, refined taste and aroma to beers containing it.

Particular hop varieties are associated with beer styles, for example true Pilseners, which are usually brewed with European (and often Czech) hop varieties such as Saaz, Hallertau, Strissel, and Spalt.

Flavours and aromas are described appreciatively using terms which include "grassy", "floral", "citrus", and "spicy". Most of the common commercial lagers have fairly low hop influence, while true pilseners should have noticeable noble hop aroma and certain ales can have high levels of bitterness.

Medicinal use

The medically active ingredients in Hops are humulene and lupulene.

Dried female buds have a high methylbutenol content, which has a mild sedative on the central nervous system; it is used in the treatment for insomnia, tensions and anxiety. If one has trouble getting sleep, hop tea before going to bed may help.

Hops' antibacterial qualities also stimulate gastric juice production.


The stem is flexible and very tough, with a tenacious fibre that has been used in some cases to make cloth and paper.

Other uses

Tender young hop shoots, which are only available for about three weeks during spring, were mainly eaten by the poor in medieval times, and was a substitute for asparagus. Only recently have they been rediscovered as a delicacy in parts of Germany, Belgium and England. They are served raw with vinaigrette, or boiled with fresh herbs or fried in batter.

Wild hops are also relished by cows, horses, goats, sheep, and pigs.

from the Household Cyclopedia

The following information of from the 1881 Household Cyclopedia.

The hop is planted on various soils, and chiefly in valleys. Hops are generally of the best quality from strong clay land. The crop, however, is there very precarious. Those on peat are much more productive, but are liable to be affected by mold in some seasons, which reduces their value considerably. The best plantations are on a deep, loamy soil, where the produce of the latter and the quality of the former are sometimes obtained. Those which are grown on sandy and gravelly lands are seldom remarkable for either great produce or superior quality.

The plant is extremely liable to disasters from its first putting up in the spring until the time of picking the crop, which is in September. Snails or slugs, ants and flies, are formidable enemies in the first instance. Frosts are inimical to its growth, and the vines are frequently blighted even after they have reached the top of the poles. Small green flies and other insects which make their appearance in the months of May and June, when the wind is about northeast, often greatly injure them, and they are subject to take damage by high winds from the southwest. The best situation for a plantation, therefore, is a southern aspect, well shaded on three sides either by hills or planting, which is supposed to be the chief protection that can be given them.

In the winter time provide the soil and manure for the hop-ground against the following spring. If the dung be rotten, mix it with two or three parts of common earth, and let it incorporate together till there is occasion to make use of it in making the hop-hills; but if it be new dung, then let it be mixed as before till the spring in the next year, for new dung is very injurious to hops. Hops require to be planted in a situation so open that the air may freely pass round and between them to dry up and dissipate the moisture, which often destroys the middle of large plantations, while the outsides remain unhurt.


  • Lee W. Janson, Ph.D.; Brew Chem 101; Storey Publishing; ISBN 0-88266-940-0 (paperback, 1996)

External links

da:Humle (Humulus lupulus) de:Echter Hopfen fr:Houblon it:Humulus lupulus lt:Apynys nl:Hop (plant) no:Humle pl:Chmiel ro:Hamei fi:Humala sv:Humle uk:Хміль zh:啤酒花


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