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Akan-Mashū NP, Hokkaido
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This roughly 100-hectare flower field lies at only about 150 m elevation, yet isotsutsuji and dwarf pine—plants associated with mountain environments—thrive here. Sulfurous volcanic gases and acidic soil help create this unusual habitat.
Hokkaido says the plant’s formal Japanese name, isotsutsuji, may come from someone mishearing “ezotsutsuji.” Despite the spelling, its “iso” is not a clue that this mountain flower belongs by the seashore.
The sulfur mountain above the colony once helped bring railways to this remote region. In 1887, a 41-km line from Iozan to Shibecha was built in just 8 months; the line was later taken over by Hokkaido and became part of today’s JR Senmo Line story.
Crowberry, or gankōran, grows among the highland plants around Tsutsujigahara. Ainu people once used its dark berries as dye; today, the berries are also made into a jam associated with this area.
The smoking volcano beside the flower field is also called Atosanupuri, an Ainu name meaning “bare mountain”—a fitting description of its exposed, rocky slopes. Its Japanese name, Iō-zan, means “sulfur mountain.”
These azaleas don’t make the pink display many people expect: their tiny white flowers gather into round, ball-like clusters, with long stamens. The leaves have a strong, herb-like scent when gently rubbed.
Along the roughly 2.5-km trail between Kawayu and Iozan, the scenery shifts from conifer forest to broadleaf woods, isotsutsuji heath, then dwarf pine. Here, the pines can stand upright instead of crawling close to the ground.
Some small red shapes on the ground along the trail are hanagoke—a lichen, not a flower. This hardy organism catches ash from Iozan and helps keep volcanic dust from mixing into Tsutsujigahara’s soil.
A 2023 park management plan records dwarf pine growing within some isotsutsuji stands and suppressing them, while other pines near vents have died. The causes were unclear and may be part of natural ecological change.
