Photography is about capturing light though lenses, but choosing the right lens for the job isn't always cut and dry. Lenses for landscape photographers can be particularly difficult to choose because the vast array of options available.
First and foremost, there is no one-size fits all, do everything lens. New photographers often look for the one lens that will do everything and then some, this doesn't exist. There are options to fit your specific needs though, and that's what we're going to explore. The real answer is 12mm-500mm, it really depends on what you're shooting and where you are in relation to it.
Size and weight are also a factor for some photographers. Because most landscape photographers are also hikers, campers and travelers, carrying around twenty or thirty pounds of gear can be daunting, so choosing faster prime lenses instead of a larger, heavier zoom lens means you won't have as much flexibility as a zoom lens provides but the trade off is a significantly lighter load to carry with you.
Fast lenses, or those with a maximum aperture of f/2.8 or faster aren't always needed either, because the sweet spot of most lenses, or where they are sharpest and perform the best, ...