Hops or Humulus is a group of flowering plants in the Cannabacea family, which incidentally includes the genus Cannabis (hemp) and Celtis (Hackberries). The hops plant produces male and female flowers on separate plants, which means they are dioecious. The female flowers, or cones, are used for several culinary purposes but most notably they are used in the brewing of beer .
The hops plant is usually referred to as a vine, but in actuality it is a bine because it uses stiff hairs on its rigid stem instead of tendrils to climb. It is a perennial plant, re-growing annually from an underground rhizome. The hops bine can grow over 20 inches in a single week and climb to heights of over 50 feet, spiraling clockwise as it climbs. If you are a gardener you will be happy to know growing hops is fairly easy and rewarding.
The hop cones impart a spicy floral aroma and a bitter flavor when used in beer brewing. Beer bitterness is expressed as IBUs or International Bitterness Units; a measure of the intensity of the bitterness in a given beer. As a point of reference here are some common beer styles and their IBU range. Alpha acids are the precursors to beer bitterness. The hops used to add bitterness to a beer are added during the boil so the heat from the boiling wort has time break down the acid.
Another way to use hops in brewing is dry hopping; the process of adding hops to the primary fermenter, the maturation tank, or the casked beer to increase the aroma and hoppy character of the finished beer. Not all hops are the same, and aside from when and where you add them, there are many different varieties of hops to choose from. The type of hops chosen can impart more than a subtle difference to the flavor and aroma of your home brew beer, so choose your palette wisely.