# Hops
**Hops** are the female flower cones (strobili) of the climbing perennial plant *Humulus lupulus* L., a member of the [Cannabaceae](https://www.edgepedia.org/cannabaceae) family, grown almost exclusively to bitter, flavor, and preserve beer[1](https://pubmed.ncbi.nlm.nih.gov/18308492/) • [2](https://www.mdpi.com/2304-8158/9/5/541). The plant is indigenous to Europe, Asia, and North America[3](https://www.mdpi.com/2673-6918/6/1/4), and its cones contain the resins, essential oils, and polyphenols that give beer its characteristic bitterness and aroma[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10534726/).
| Key fact | Detail |
|---|---|
| Botany | *Humulus lupulus* L., family Cannabaceae; a climbing perennial whose commercially valuable product is the unfertilized female inflorescence, the hop cone[1](https://pubmed.ncbi.nlm.nih.gov/18308492/) • [2](https://www.mdpi.com/2304-8158/9/5/541) |
| Growth | Shoots can grow up to 30 cm a day; plants reach seven to nine meters, grown vertically on strings or wires for sunlight[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage) |
| Brewing chemistry | Alpha acids in the lupulin glands thermally isomerize into bitter, water-soluble iso-alpha-acids during wort boiling; essential oils supply aroma[6](https://www.mdpi.com/2304-8158/15/8/1358) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10534726/) |
| Varieties | More than 260 varieties are available, differing in alpha acids, essential oils, and polyphenols[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC10534726/) |
| Production | The EU grows hops on 26,500 ha (60% of world area) and produces about 50,000 tonnes annually; Germany accounts for 17,000 ha[7](https://agriculture.ec.europa.eu/farming/crops/hops_en) |
| Historical law | The 1516 Bavarian Reinheitsgebot permitted only barley, hops, and water in beer[8](https://www.hopfenforschung.de/en/all-about-hops/history/) |
| Other uses | Traditional medicine for sleep disturbances; hop extracts and oil are assessed as safe for use in cosmetics[1](https://pubmed.ncbi.nlm.nih.gov/18308492/) • [9](https://pubmed.ncbi.nlm.nih.gov/38126727/) |
## Plant and chemistry
The hop cone is a modified stem and leaf structure that protects the female flower cluster[10](https://extensionpubs.unl.edu/publication/ec3050/cultivating-hops-for-cone-production-in-nebraska). Its commercially important constituents sit in the lupulin glands, yellow granular oily resins at the base of the cone scales[11](https://ucanr.edu/?legacy-file=294701.pdf&legacy-file-path=sites%2FSFA%2Ffiles%2F). Three groups of compounds matter to brewers: the bitter resins, the essential oils, and the polyphenols[12](https://www.bicga.org.uk/docs/Principles_of_Cereal_Science_and_Technology.pdf).
**Bitterness.** The alpha acids, principally humulone and its analogs, are by far the most important constituents of hop resin[13](https://www.sciencedirect.com/science/article/pii/S1373716310001769). Boiled with the wort, they undergo thermal isomerization into iso-alpha-acids, the bitter, water-soluble compounds that balance malt sweetness; the yield depends on hop variety and timing of addition[6](https://www.mdpi.com/2304-8158/15/8/1358). Hop prices are expressed as a function of alpha-acid content, a measure of the class's commercial importance[14](https://www.sciencedirect.com/science/article/pii/S0308814614015258).
**Aroma.** The essential oil is a highly complex mixture of hundreds of volatile compounds[6](https://www.mdpi.com/2304-8158/15/8/1358). Key aroma contributors identified by sensomic analysis include linalool, geraniol, β-myrcene, 2-undecanone, and [methyl decanoate](https://www.edgepedia.org/methyl-decanoate)[15](https://www.sciencedirect.com/science/article/pii/S0308814624020983). Because volatile compounds dissipate during boiling, hops added late in the boil or during fermentation (dry hopping) give a markedly more pronounced hop aroma than kettle additions[6](https://www.mdpi.com/2304-8158/15/8/1358). The aroma of raw hops does not necessarily predict the hoppy aroma of the finished beer, since brewing yeast can biotransform geraniol and release geranyl esters and polyfunctional thiols[16](https://www.tandfonline.com/doi/full/10.1080/03610470.2023.2232267).
## History
Wild and cultivated hops were found across central and northern Europe in the early Middle Ages and have been used to prepare beer since the 9th century[17](https://www.hopfenforschung.de/wp-content/uploads/2023/07/Proceedings_STC_2023.pdf). The Hallertau region of Germany is the first known place of hop cultivation, in the 8th century, and the first document-based evidence there dates to the 9th century[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage) • [8](https://www.hopfenforschung.de/en/all-about-hops/history/). Hops were presumably first added to beer not for taste but for their antibacterial effect, which extended shelf life; the scholar Hildegard von Bingen wrote in 1160 that hop's bitterness "prevents the rot"[8](https://www.hopfenforschung.de/en/all-about-hops/history/). Use of hop flowers in brewing drove worldwide cultivation in hop gardens from the 11th century on[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage).
In 1516 the Bavarian Reinheitsgebot of Dukes Wilhelm IV and Ludwig X defined hops, alongside barley and water, as the only permitted beer ingredients[8](https://www.hopfenforschung.de/en/all-about-hops/history/). Hops were cultivated in the [Low Countries](https://www.edgepedia.org/low-countries) from the 13th century and were probably introduced from Flanders to Kent in England at the end of the 15th century[18](https://www.britishhops.org.uk/hops/history/). English brewers initially imported dried Flemish hops of such poor cleanliness that a 1603 Act of Parliament imposed penalties on dealing in hops adulterated with "leaves, stalks, powder, sand, straw and with loggetts of wood dross"; at that time hops were valued solely for preserving beer, with the bittering effect reluctantly accepted[18](https://www.britishhops.org.uk/hops/history/). A 1710 Act prohibited any bittering agent other than hops in beer[18](https://www.britishhops.org.uk/hops/history/). By the 17th century unhopped ale had lost popularity, and by 1655 hop cultivation had grown rapidly across fourteen English counties[18](https://www.britishhops.org.uk/hops/history/).
## Cultivation and harvest
Hops are not grown from seed commercially; cultivars are propagated vegetatively, by rhizomes or stem cuttings, to maintain cone chemistry and other cultivar characteristics[19](https://extension.oregonstate.edu/es/catalog/em-9115-growing-hops-home-garden). Growth and flowering are influenced by daylength, and the plant flourishes with good nutrition and water[11](https://ucanr.edu/?legacy-file=294701.pdf&legacy-file-path=sites%2FSFA%2Ffiles%2F). For centuries the harvest in late August and September was done by hand and was highly labor-intensive; workers, including whole families who migrated from cities such as London and [Birmingham](https://www.edgepedia.org/birmingham) for the season, removed the bines, cut the tendrils, and sorted flowers from leaves[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage). A mechanical hops separator was invented in 1909, and in Britain the first hop-picking machine was imported in 1922, with machine picking becoming widespread only in the late 1950s[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage) • [18](https://www.britishhops.org.uk/hops/history/).
Hop growing has always been risky: the plants need much care, and quality and quantity vary considerably with climate[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage). [Powdery mildew](https://www.edgepedia.org/powdery-mildew) is one of the most important hop diseases and, if unmanaged, can cause complete loss of the marketable crop; susceptibility varies widely among varieties, so planting resistant cultivars is the most efficient control[20](https://extension.oregonstate.edu/catalog/em-9256-managing-powdery-mildew-hop-best-practices).
## Production and market
The European Union has about 2,600 hop farms covering 26,500 hectares, 60% of the world's hop-growing area, and produces about 50,000 tonnes of hops annually, with alpha-acid output regularly exceeding 5,000 tonnes[7](https://agriculture.ec.europa.eu/farming/crops/hops_en). Germany is the largest EU producer with 17,000 hectares, about one third of world hop area, followed by Czechia, Poland, and Slovenia[7](https://agriculture.ec.europa.eu/farming/crops/hops_en). Annual world production varies between 80,000 and 100,000 tonnes, corresponding to 8,000 to 10,000 tonnes of alpha acid; demand is estimated at about 8,000 tonnes, based on an average of 4.1 g of alpha acid per hectolitre of beer[7](https://agriculture.ec.europa.eu/farming/crops/hops_en). Because higher-yielding alpha-acid varieties and consumer preference for less bitter beer have reduced hop content per hectolitre (6.3 g alpha per hectolitre in 1995), acreage is dwindling and prices have been fairly low since 2009[7](https://agriculture.ec.europa.eu/farming/crops/hops_en).
In the United States, 2024 production totaled 87.1 million pounds, down 16 percent from 2023, on 44,793 harvested acres, down 18 percent, with a yield of 1,944 pounds per acre and a production value of $446 million[21](https://www.nass.usda.gov/Statistics_by_State/Regional_Office/Northwest/includes/Publications/Hops/2024/hops1224.pdf). A 2025 industry report put German acreage at 18,962 hectares, down 6% year on year, and global production at 109,188 metric tonnes[22](https://hops.com.au/barthhaas-report-2025-2026/?hilite=motueka).
## Varieties and classification
Brewers classify varieties by alpha-acid content and use. One scheme sorts hops into bitter types with an α/β ratio of 2:1 or 3:1 and 10–20% alpha acids, aromatic types at roughly 1:1 with 2–10% alpha acids, and mixed types[23](https://www.mdpi.com/2223-7747/15/18/2817); another common split places bitter hops above 7% alpha acids and finishing or aromatic hops below[2](https://www.mdpi.com/2304-8158/9/5/541). Fine aroma varieties such as the Saaz group run 5 to 7 wt% alpha acids, cohumulone below 30% relative, and about 1.0 wt% hop oil[24](https://www.mdpi.com/2306-5710/10/3/90). Both genetic background and growing region shape volatile composition and aroma potential[3](https://www.mdpi.com/2673-6918/6/1/4). Since 2012, the number of varieties in commercial use has grown from 180 to 250, driven by craft brewers choosing hops for taste rather than yield alone[5](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage).
## Other uses
Hop female inflorescences have long been used in traditional medicine, mainly to treat sleep disturbances, and traditional applications as a stomachic, antibacterial, and antifungal remedy have some in vivo or in vitro support[1](https://pubmed.ncbi.nlm.nih.gov/18308492/). Among hop prenylated chalcones, xanthohumol has shown cancer chemopreventive activity in vitro, and 8-prenylnaringenin has been characterized as one of the most potent phytoestrogens isolated to date[1](https://pubmed.ncbi.nlm.nih.gov/18308492/). The Cosmetic Ingredient Review Expert Panel concluded that hops extract and hops oil are safe in cosmetics within present practices of use when formulated to be non-sensitizing, while flagging constituents of concern including 8-prenylnaringenin, β-myrcene, and quercetin[9](https://pubmed.ncbi.nlm.nih.gov/38126727/).
## References
1. [Zanoli & Zavatti (2008). Pharmacognostic and pharmacological profile of Humulus lupulus L. Journal of Ethnopharmacology](https://pubmed.ncbi.nlm.nih.gov/18308492/)
2. [Brewing Quality of Hop Varieties Cultivated in Central Italy, Foods (MDPI)](https://www.mdpi.com/2304-8158/9/5/541)
3. [Characterization of Volatile Compounds in Amarillo, Ariana, Cascade, Centennial, and El Dorado Hops, MDPI](https://www.mdpi.com/2673-6918/6/1/4)
4. [Effects of Dry-Hopping on Beer Chemistry and Sensory Properties—A Review, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10534726/)
5. [Traditional beer brewing: Hop's horticultural heritage, Europeana](https://www.europeana.eu/en/stories/traditional-beer-brewing-hops-horticultural-heritage)
6. [Research Progress on Raw Materials, Adjuncts, and Flavor Formation in Craft Beer, Foods (MDPI)](https://www.mdpi.com/2304-8158/15/8/1358)
7. [Hops, European Commission, Agriculture and Rural Development](https://agriculture.ec.europa.eu/farming/crops/hops_en)
8. [History, Gesellschaft für Hopfenforschung (Hopfenforschung)](https://www.hopfenforschung.de/en/all-about-hops/history/)
9. [Safety Assessment of Hops as Used in Cosmetics, PubMed](https://pubmed.ncbi.nlm.nih.gov/38126727/)
10. [Cultivating Hops for Cone Production in Nebraska, Nebraska Extension](https://extensionpubs.unl.edu/publication/ec3050/cultivating-hops-for-cone-production-in-nebraska)
11. [Growing Hops on the North, University of California ANR](https://ucanr.edu/?legacy-file=294701.pdf&legacy-file-path=sites%2FSFA%2Ffiles%2F)
12. [Principles of Cereal Science and Technology (hop components chapter)](https://www.bicga.org.uk/docs/Principles_of_Cereal_Science_and_Technology.pdf)
13. [Hop α-acids isomerisation and utilisation: an experimental review, ScienceDirect](https://www.sciencedirect.com/science/article/pii/S1373716310001769)
14. [Chemical transformations of characteristic hop secondary metabolites in relation to beer properties, ScienceDirect](https://www.sciencedirect.com/science/article/pii/S0308814614015258)
15. [Characterization of the key aroma compounds in different varieties of hops by application of the Sensomics approach, Food Chemistry](https://www.sciencedirect.com/science/article/pii/S0308814624020983)
16. [A Free Exhaustive Literature Review on Hops, Journal of the American Society of Brewing Chemists](https://www.tandfonline.com/doi/full/10.1080/03610470.2023.2232267)
17. [Genetic diversity of European wild hops in a historical context, Scientific Technical Commission proceedings](https://www.hopfenforschung.de/wp-content/uploads/2023/07/Proceedings_STC_2023.pdf)
18. [History of Hops, British Hop Association](https://www.britishhops.org.uk/hops/history/)
19. [Growing hops in the home garden, Oregon State University Extension](https://extension.oregonstate.edu/es/catalog/em-9115-growing-hops-home-garden)
20. [Managing Powdery Mildew in Hop: Best Practices, Oregon State University Extension](https://extension.oregonstate.edu/catalog/em-9256-managing-powdery-mildew-hop-best-practices)
21. [National Hop Report, USDA NASS, December 2024](https://www.nass.usda.gov/Statistics_by_State/Regional_Office/Northwest/includes/Publications/Hops/2024/hops1224.pdf)
22. [BarthHaas Report 2025/2026, Hops Products Australia](https://hops.com.au/barthhaas-report-2025-2026/?hilite=motueka)
23. [A Comprehensive Study of Hops (Humulus lupulus L.): Botany, Phytochemistry, Cultivation, and Industrial Uses, Plants (MDPI)](https://www.mdpi.com/2223-7747/15/18/2817)
24. [SAAZ—Fine Aroma Hop Pedigree: A Review of Current Knowledge, Beverages (MDPI)](https://www.mdpi.com/2306-5710/10/3/90)
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