A friend of mine has a large grape vine in his back yard. I picked a bag of leaves, thinking that I would make dolmades or maybe try to braise them like you would collard greens. Unfortunately, I have no idea why kind of grape fine it was. All I know is that the grapes were purple and the leaves were green.
When the leaves were raw, they tasted fine and seemed edible. After blanching them, they became extremely tough, unchewable. When I tried to eat one, it felt like chewing paper--my teeth couldn't bite through it, it just mashed into a tight ball in my mouth.
I even tried braising some of the leaves for an hour or two and they were still unchewable.