When making bitters, measure the liquid (a neutral grain spirit) in fluid ounces, and measure the solids by weight. The ratio of liquid to solid should be 2 to 1 for fresh ingredients and 4 to 1 for dry ingredients. Commercial bitters often have long lists of ingredients, but I prefer to use just 3 to 5 in my foraged bitters, so the flavor of each can be fully appreciated. At least half of the solids should be bitter; the remainder can be a combination of spice and fruit, depending on your personal preference. In this recipe, I use both yarrow root (for the primary bitter ingredient) and yarrow leaf (the spice).
The ABV (alcohol by volume) of commercial bitters ranges from 37 to 45 percent. By combining equal parts of your alcohol- and water-based infusions, your bitters have an ABV of 37.5 percent.