This is my view cut and pasted from a recent almost identically named thread:
Generally speaking a wide angle is useful in landscape photography for recording some interesting foreground feature, such as a rock for example. A good landscape photograph generally includes an interesting foreground, middle ground and background, that's why they are so popular. A telephoto lens is really useful for 'compressing' the perspective of a hills, valleys trees etc. Another general rule of the thumb is that most landscapes are better photographed using a smaller aperture, typically around f/11 - f/16 to create greater depth of field (front to back sharpness). In short, there is no best lens for landscape photography. The same vista could be photographed using two different lenses, the perspective would be entirely different, but that's where knowledge of focal lengths will come in useful so that you can visualise the 'final' image.