I have done some research on gruit and basically it comes down to three herbs: Juniper Berries, Elderberries, and rosemary. Juniper Berries were a source of yeast, as it settled on the berry randomly and openly. The reason thaqt gruit is thought to be these three specific herbs was that these herbs were taxed by the government and only certain deligates were appointed to grow them for brewin purposes and that records dating back only mention these for brewing. This is also partly the reason hops were forbidden in brewing.
However, the use of other herbs and hops were used interchangibly as a result of the lack of Gov't regulatory reach. They could not control individual households on what they included in their own personal brew. Eventually, regulations regarding purity (Rheinhotsgebhot) and health as well as importation of beer from other countries (and the ease of growing hops in Germania) helped hops become the mainstay in the industry.
As you will see I use some other herbs as well. Here is an awesome Stout recipe brewed with Gruit taken from
gruitale.com :: Gruit Ale & Unhopped Beers, Brewing Herbs and Recipes. It is a cool site as well. Check it out.
8 1/2 lbs pale 2-row malt
3/4 lb caramel 120 L malt
1/2 lb chocolate malt
3/4 lb Weyermann Carafa II malt
1/2 lb roasted barley
1/2 lb Weyermann pale wheat malt
1 lb oat flakes
Extra sugars
2 lbs wildflower honey
1 c blackstrap molasses for bottling
Herbs
1 1/2 oz dried mugwort tops and leaves (roughly three packed cups)
1/2 oz licorice root
1/2 oz roasted chicory root
1/2 oz dried chamomile flowers
1/4 oz dried lemon grass
1/4 oz dried sweet orange peel
1/2 fl oz vanilla extract
1 T Indian sarsaparilla (Hemidesmus indicus)
Yeast
Wyeast Scottish Ale
- WW