Hops

Hops are the cone-shaped flowers of Humulus lupulus, a perennial climbing bine in the Cannabaceae family. They are the single ingredient most responsible for what makes a beer an IPA, contributing bitterness, flavor, aroma, and a measure of microbial stability. No hops, no IPA.

#The Plant

Hops grow as bines — climbing stems that wrap clockwise around a support, distinct from true vines, which use tendrils. Commercial hop yards train the bines up coir twine on trellises 18 feet (5.5 m) tall. The plant is dioecious: male and female plants are separate, and brewers harvest only the unfertilized female cones, because seed development dilutes the prized resins. The plant is photoperiod-sensitive, thriving in a narrow band of latitude roughly 35°–55° in both hemispheres — see Hop Growing Regions.

#The Cone and the Lupulin

A hop cone (strobile) is a layered cluster of papery green bracts and bracteoles arranged around a central strig. Tucked at the base of the bracteoles are tiny golden-yellow glands of lupulin — a sticky resinous powder that is the brewer's true prize.

The chemistry of these compounds is the subject of Hop Chemistry, with bittering covered in Alpha Acids and Bitterness and aroma in Hop Oils and Terpenes.

#What Hops Do for an IPA

Timing is everything: the same hop boiled hard yields clean bitterness, while added cold in the dry hop yields pure aroma. See Hop Additions and Timing and Bittering, Flavor, and Aroma Hops.

#Varieties

Modern brewing draws on hundreds of cultivars. Classic American "C-hops" — Cascade, Centennial, Citra — built the West Coast IPA; newer tropical varieties like Mosaic, Galaxy, and Sabro define the New England IPA. Traditional Noble and English Hops anchor the English IPA. Browse them all in the Hop Variety Index.

#Continue Reading

• Hop Chemistry — the compounds inside the cone
• Hop Products and Formats — how brewers buy hops
• Hop Growing Regions — where hops come from
• Hop Variety Index — the full catalog of varieties