Hops

• Scientific name: Humulus lupulus
• Family: Cannabaceae (hops, cannabis)

Hardy, twining, herbaceous perennial. Stem rough, produces a milky latex sap. Leaves 3-5 lobed, oppositely arranged, coarsely toothed. Plants either have male or female (dioecious) flower cones (inflorescences). Male inflorescences panicles; female inflorescences round spikes, both with papery bracts. Fruits much larger than inflorescences, spherical, straw-coloured. Pollinated by wind.

• Hops can be grown in different ways: on hop hills (on 10-foot tall posts in a mound of compost) up sisal strings suspended from wires attached to chestnut posts trained by ‘butchers’ and ‘umbrella’ and ‘Worcester’ methods. Hop workers used to wear stilts to sort the wires out.
• Hops are susceptible to several pests and diseases and often require spraying.

Where it grows

Hops, like barley, come from South-East Asia, and have been used in beer for the last 10,000 years. In Europe they have been used since the 9th century and in Britain since the 15th century. They are now are grown across the Northern Hemisphere. They generally require an average summer temperature of 16–18°C, but do well over a wide range of soils provided they are fertile and moisture-holding: light to heavy loams are best.

Today the ale keeps anyway due to high hygiene standards but hops are still used for the characteristic bitter taste, flavour stability and retention of the foamy head on top. Globally unfertilised flowers are used in brewing and are produced in an all-female ‘nunnery’ hop gardens. Hop production in Britain differs in that male hops are allowed in at a ratio of 1-to-200. This was a very early form of biological control! Under Britain’s particular climatic conditions the unfertilised stigmas were a focus for powdery mildew infection. Pollination led to the stigmas on the female flowers withering rapidly, reducing the chance of infection.

Useful links

• Blog about urban hop production
• Campaign for Real Ale

Glossary

• Bract: modified or specialised leaf in a flowering structure (inflorescence).
• Herbaceous: possessing characteristics of herbs. Loam: well-drained soil composed mainly of sand and clay.
• Lobe: incomplete division in any plant organ (eg leaf).
• Panicle: branched flower stalk.
• Perennial: lives for at least two years.