Gruit is primarily a combination of three herbs: sweet gale (Myrica gale), yarrow (Achillea millefolium), and wild rosemary (Ledum palustre). Additionally, individual brewers would add other herbs and spices as they liked to produce unique flavors and aromas in their beer. These herbs were known for their mildly stimulating properties, and when added to fermented beer were known to have said inebriating qualities amplified.