Brewing beer at home affords one a unique opportunity to experiment with beer. Brewing with herbs and spices opens your beers to an infinite variety of flavors and inebriatory enhancements. This is an often unspoken of and obscure practice due to a historical prejudice and prohibition against any herb that is not hops being used in beer. This need not be the case today, however, and even large scale breweries are using a variety of different and non-traditional admixtures in their beers, from goji berries to peppers to hazelnuts.
Creativity is everything to making home brew. Even from your first batch of beer, there can be unexpected elements thrown into the wort. Some of these elements can been symbolic with pleasurable results, and some will have to be poured out. When you use non-traditional methods and ingredients in your brew, you have to be ready for any of these results or some even stranger.
When experimenting with herbs and spices, it is a good idea to ask the advice of someone knowledgeable about herbs. Many herbs, including hops, have powerful qualities, which classify them as medicinal. If you have an ill-advised ingredient in your beer, someone may become sick from drinking it. So make sure that you know what you are putting into the beer.
Stephen Buhner's book, Sacred and Healing Herbal Beers, is thought to be a sort of unofficial bible for alternative brewing. This book contains many recipes culled from the annals of brewing history, and includes the mythology and folklore surrounding many of the brews. This book is for reference purposes only, and puts forth many great ideas about different herbs and spices that have been used in beer. Although many of these ideas may seem non-traditional, in the sense of the current tradition of brewing, some have deep roots in cultural traditions that go back before the German Beer Purity law.
Another series of books to enhance your brewing style is the Pharmako Poeia, Pharmako Dynamis, and Pharmako Gnosis books of Dale Pendell. These brewing books present a unique perspective on understanding the personality types of different herbs and plants, even of yeast. This series of books is more on the spiritual side of things, and if you look at the brewing process in an alchemical light, they can be quite useful for your experiments.
This article is just a preface and too short to go into much detail about which herbs and spices to use with which kinds of beer, but one important note is that different qualities emerge from different parts of different plants at different extraction levels. For example, you can get certain qualities out of a plant by boiling it (such as tea). But you may get a different quality from an alcohol extraction. You may also get an even different quality from using a high potency alcohol as opposed to a low potency one (a brewer's range goes from roughly 3% to 12% alcohol, and there is even difference in the extractive qualities at this low level of alcohol).
Another factor to consider is that many of the aromatic qualities of herbs that are used in brewing will disappear at temperatures higher than 70 degrees. This is true as well of the aromatic qualities of the malt that is used in the brewing process. By monitoring the temperature of the wort and keeping it just below the boiling point, you can make a sort of 'raw ale' that is more flavorful than beer made form boiled wort.
We can see a trend in even large-scale breweries towards a more open-minded approach to home brewing, and brewing ingredients in the last few years. New Belgium is a prime example of this with their Springboard Ale, which contains a variety of uncommon ingredients, including wormwood, goji berries and schisandra, along with oats and Mount Hood hops. From Rogue Brewery, we see a wonderful hazelnut beer, as well as a chipotle ale and a mocha porter. It certainly is heartening and inspiring to see such successful breweries experimenting and producing inventive and tasty drinks on a large scale.