Handsome, I see from your location, that you are a doctor, so I am inclined to believe your description. Well, even without your description, I sing, "Google loves me, this I know, it's search engine tells me so. Poison things to me it shows, so I won't quit while the world goes." OK, not a very good song, but hey, it's Google.
http://www.formaggiokitchen.com/shop/product_info.php?products_id=1535
I never knew that Sumac was edible..., just that as kids, we would smash it's bunches of bright, dark berries, and smear it on our skin, and get the tar waled out of us for getting our skin and clothes died. I could have told them it wasn't tar, but nobody listens to kids. In a strange twist of fate, staghorn sumac was used medicinally to help staunch bleeding -- which explains why I'm still alive after having my hide removed.
http://www.bio.brandeis.edu/fieldbio/medicinal_plants/pages/Staghorn_Sumac.html
There's lots of types. This is NOT what our prevalent type is
http://www.thekitchn.com/thekitchn/ingredients-fruit/have-you-tried-sumacade-092887 -- ours has stalks of purple berries and makes a wonderful, long-lasting skin die. Your skin will turn deep reddish-purple and last for days or at least several spankings.
FINALLY found it... it wasn't SUMAC that got us sore-tailed, but POKE BERRY.
http://wilderix.wordpress.com/2007/05/15/poke-aint-no-joke/.
What the heck can I do with pokeweed? I mean, aside from getting severe stomach cramps, nausea and vomiting, and diarrhea. I think I'll pass...