This stuff is super good....I have made it.
First and important, be sure you using common sumac berries and not those of poison sumac. One you locate sumac in the berry stage, pick what you need according to this recipe...
1 quart of sumac berries
1 gallon water
maple syrup or honey (to taste, optional)
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How to make it:
Bring water to a boil
Place sumac in a large teapot or non-metal container
Pour boiling water over the sumac
Steep for 20minutes - 2 hours
Strain through cheesecloth or a coffee filter
Enjoy over ice