Humulus lupulus and Japanese hops. Humulus japonicus

Hops are native to temperate regions of Europe, North America and Asia, being one of two species in the Cannabaceae family. Some of the earliest records of beer being made with hops was from the Middle Ages around 822. During this time beer was a popular beverage, and hop cultivation rapidly spread throughout Europe. The first commercial hops crop established in the US was in 1808. Hops are now cultivated in many countries around the world.

Hops are a perennial vine, with the seedless hops which have been prevented from pollinating considered more desirable with brewers. Hops are capable of growing in a wide range of climates and require good drainage and full sun. Being a vine and capable of reaching 10 meters in height, some form of trellis is required to support the plant. Only the female flowers or hop cones are used in brewing.

Hops serves several purposes in brewing beer. The hops not only add to the bitterness of a beer, they also add aroma, used as a clarifying agent, contain mild antibiotic properties which helps prevent the brew from going off, and helps the end product retain a good head when served.

Simplistically, beer can be categorised into two categories, lagers and ales. The main difference between a ale and lager is that ales are fermented quickly with top fermenting yeasts and high temperatures, while ales are bottom fermenters at lower temperatures and at a slower rate. This is a general categorisation of the different types, not all beers fit into these categories. Hops have two basic distinctions. Bitter or kettle hops, which are added at the beginning, creating the bitter flavour. Aroma or finishing hops which are added at the near the end of brewing to give it aroma. 

Apart from being one of the key ingredients in beer making, hops has other uses as well. The young shoots can be eaten as a vegetable, and hops has many medicinal uses such as sleep pillows which help people with insomnia. Being a vigorous climber, some species of hops are prized ornamental plants which have variegated and colourful foliage.