On the debate on Vinland and grapes:
The actual word in the sagas is "vinber" which means a berry used to make wine. It doesn't necessarily mean "grape". People made wine out of elderberries, gooseberries, currants, and many other berries that grow as far north as Newfoundland.
Helge Ingstad points this out in his book about his and Anne Stine's discovery of the L'Anse Aux Meadows Norse settlement site. Gwyn Jones also talks about it at length in his books about the Vikings.
Samuel Eliot Morison says that this was first pointed out by Merritt L. Fernald, a botany professor at Harvard, in 1910. (Poor Professor Fernald, I don't even have the urge to link your name -- you are too obscure sounding...)
Even before the Vinland Sagas were written down, Adam of Bremen, in 1075, referred to Vinland as the land of wild vines that yield excellent wine.
But even if, in 1075 or so, rumor had it that there were vines with berries on them in Vinland, it could easily have been just misinformation based on people's extrapolation of that fatal word "vinber".