 Several species of willow ("Salix") form a large component of the native small shrubbery on the archipelago.These include rock willow ("Salix vestita"), bog willow ("S. pedicellaris"), and Labrador willow ("S. argyrocarpa"), as well as naturally occurring hybrids between "S. arctica" and "S. glauca".Other than in valley regions, trees cannot grow on the islands because of a lack of adequate soil.