Without a doubt, hops are the hot ingredient in the craft beer world right now. That hasn't always been the case, though.
Hopheads are perhaps loathe to admit it, but it is possible to brew without them. For the first several thousand years of the history of beer, brewers used other plants to provide bittering and flavors. In post-Roman Europe, the beverage became known as gruit.
Three herbs formed the core of most gruits: bog myrtle (known interchangeably as sweet gale), yarrow and wild rosemary. Bog myrtle was the most desirable plant for adding bitterness to the brew, while yarrow was used for its aromatic properties. Wild rosemary also provided bitterness, but it's mildly toxic and has some hypnotic effects, perhaps explaining its enduring popularity at the time.
In addition to those core herbs, brewers sometimes used other locally available plants for bittering. Unfortunately, the motivation for doing so often was to save money, which occasionally resulted in poisonous plants making it into beer.
Gruit entered a decline around the year 1100 when hops came on the scene in Germany. The transition was accelerated by laws such as the Reinheitsgebot, which effectively banned the use of gruit herbs partly out of health concerns but more significantly because hops were a more easily taxed commodity. The supply of gruit herbs was controlled by the Catholic Church in many places, so it was out of reach for local governments. Hops had no such baggage.
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