Alpine Arnica is a well known medical plant but it is very difficult to keep in the garden. If your soil is not completely free of lime you need not bother a try. Also commercial herb farmers have great difficulties to grow Alpine Arnica. Even today most Arnica is collected in the wild. Fortunatelly there is also an American relative of the Alpine Arnica with the same active pharmaceutical ingredients (although in lower concentration): the Chamisso Arnica. It is not fussy at all, all it asks for is a moist suny spot.