I'm not sure why it disturbed me to pour out the Sioux City Birch Beer into a glass and found that it was red and not brown like the Root Beer and Sarsaparilla.
According to my knowledgeable friend Wikipedia, red is within the range of birch beer colors, which are the result of the different species of birch trees from which the sap is taken.
Wait ... sap? Not roots? Nope, it's sap, and wikipedia also suggests sucking on a broken birch tree twig to taste the birch beer flavor.
I think I'll just take their word for it.