Alpine Flora on Dewa Sanzan
An abundance of alpine flora grows on Mt. Gassan (1,984 m) in the Midagahara High Moor, located along a plateau formed by lava flow on a gentle slope on the peak’s northeastern side, at around 1,400 meters.
The natural environment differs significantly from one side of the ridgeline to the other. The steep, windy western side, which faces the Sea of Japan, has dry soil. These conditions attract plants that cling to rocks, including komebatsuga-zakura (Arcterica nana) and the pincushion plant (Diapensia lapponica). On the gently sloping eastern side, dense snowpack melts slowly, leaving the ridge damp and creating a marsh-like terrain. Plants such as daylilies (Hemerocallis dumortieri), hina-zakura (Primula nipponica Yatabe), and round-leaved sundew (Drosera rotundifolia L.) thrive here. These two sides are separated by a plateau, which can be crossed by a wooden boardwalk. From July to August the plateau blooms with white-flowering miyama usuyukiso (Leontopodium fauriei), and hairyflower bellflower (Campanula chamissonis). Some particularly notable species are Ezo no hakusan ichige (Anemone narcissiflora var. sachalinensis), a flower that grows only in Hokkaido and on Mt. Gassan, and Oze kohone (Nuphar pumilum var. ozeense).
The snowpack on Mt. Gassan can reach 30 meters deep, and parts of the mountain remain covered in snow into late August. The alpine plants start to bloom in early summer as the snow melts. This melt is very gradual, which staggers each species’ flowering season to the extent that a single species can be in its spring, summer and autumn stages at different locations across the marsh. Alpine flowers bloom on Mt. Gassan from June to September.
Alpine zones such as this typically occur at 2,500 meters and above, but alpine flora on Mt. Gassan grows at around 1,300 meters. It is, therefore, referred to as a “pseudo alpine zone,” a rare phenomenon that occurs when particularly harsh conditions create an environment more common at higher elevations. On Mt. Gassan, strong westerly winds from the Sea of Japan and deep snowpack for much of the year make the environment inhospitable for the tall coniferous trees that would otherwise grow at this elevation.