What foodstuffs did northern European nations, ones frequently experiencing a cold year-round climate, produce? Which crops were able to survive the climate? What sort of commodities did these nations produce (for example, in the game Civilization, Scandinavia, when "true" resources are activated, are rich in truffles; is there any basis to this?).
I can't say much about the other Scandinavian countries but Norway mostly farmed potatoes and caught fish. Even if there had been a better climate for farming Norway has very little arable land (about 3% left over from when Norway was pushed into the sea by glaciers during the ice age, so nearly exclusively by the coast.) they traded mostly in wood (mainly for British ships.) and ice (not sure how big the ice trade was but it was mentioned in class.)
Source: I live in Norway and learnt this in history and geophysics classes.