I shoot mostly landscapes on 6x7 medium format.

Reckon I use these lenses in order of use for landscapes (all lenses are given as their 35mm equivalent): 35mm, 50mm, 150mm, 28mm. For macro close-up nature patterns etc I use a macro lens. Intereseting as the 28mm is usually seen as the 'landscape photographers' lens but I often find it too wide, I like the perspective of the 35mm a lot better. At first I even had a 24mm lens but sold this as it was way to wide for how I see the world.

I also use a 617 pano and found the more common 90mm (roughly equivalent to about 28mm) too wide and use a 150mm lens which is equivalent to a wide standard.

You should try as many different focal lengths from friends cameras etc and see which suits your shooting style best.

Hope this helps.